Reviving the G20

Executive Summary

The G20 again stands at a crossroads. When the United Kingdom hosted the London Summit in 2009, a common financial emergency created unusually strong incentives for the major economies to act together. The UK helped connect political leadership to the operational capacities of the IMF, multilateral development banks and other international institutions, helping establish the G20 at leaders’ level as a central forum for global crisis management (G20, 2009; Prime Minister’s Office, 2025). In 2027 the problem is different. The need for cooperation is intensifying, but geopolitical rivalry, geoeconomic fragmentation and divergent national priorities are making comprehensive G20 agreement harder to achieve.

This paper recommends that the UK use its 2027 G20 Presidency to establish a practical three-tier operating architecture: consensus where possible; broad consensus where feasible; and problem-specific pivotal-power coalitions where necessary. Pivotal powers are the countries whose participation and capabilities are especially important to solving a particular problem. They may be G20 members or non-members, and the relevant constellation will differ across climate transition, sovereign debt, AI governance, development finance, critical minerals, supply chains and other challenges.

The proposal does not abandon consensus or create majority rule. Consensus should remain the preferred basis for G20-wide commitments. The 2025 Johannesburg precedent suggests that, where consensus is unavailable, an overwhelming majority can proceed without imposing obligations on dissenters (Cocks et al., 2025). But broad consensus is still insufficient when ambition must be diluted to attract near-universal support. In such cases, the G20 should identify the countries whose cooperation is functionally pivotal, convene them, mobilise the relevant international organisations, support implementation and formulate agreements so that additional countries can accede later on transparent and non-discriminatory terms. Crucially, the greater freedom of a smaller coalition to act must be matched by responsibility toward those outside it: G20-supported pivotal-power coalitions should seek to solve global problems without shifting material social, economic, security or environmental harms onto non-participants, and should prevent, cease, repair, restore or otherwise rectify such harms wherever reasonably feasible.

This would give the UK a distinctive role in global problem-solving. Rather than measuring the Presidency primarily by the breadth of language negotiated in a final communiqué, the UK could demonstrate how the G20 can generate effective cooperation despite political fragmentation. The approach directly supports emerging UK priorities concerning secure and resilient growth, financial stability, sovereign debt, development finance, fair trade and investment, climate and clean energy, and digital development and AI (HM Treasury, 2026; Prime Minister’s Office, 2025; FCDO, 2025, 2026a; HM Government, 2024). If the UK can establish this coalition pathway as a legitimate and repeatable G20 practice, its 2027 legacy could be institutional rather than merely agenda-specific: a G20 able to convert disagreement into differentiated but expanding collective action and thereby revive itself as an effective institution for a fragmented world.

1. The G20 at a Crossroads: 2009 and 2027

In 2009 the G20 stood at a crossroads. The global financial crisis exposed the inadequacy of nationally fragmented responses to a system-wide emergency. At the London Summit, the United Kingdom helped bring together the major advanced and emerging economies with the principal international financial institutions. Leaders agreed measures to restore growth, resist protectionism, strengthen financial regulation and mobilise more than $1 trillion through the IMF, multilateral development banks and trade-finance facilities (G20, 2009). The G20’s value lay not simply in producing a declaration, but in connecting political agreement with institutions capable of implementation.

Yet the G20 did not sustain the exceptional effectiveness of 2009–10. Once the immediate financial emergency receded, several shortcomings became increasingly apparent. Its agenda expanded faster than its capacity to prioritise and implement; commitments were often weakly monitored or incompletely executed; macroeconomic coordination became less consequential; and the forum struggled to arrest protectionism or deliver decisive collective action on subsequent systemic challenges, including the COVID-19 pandemic, sovereign-debt vulnerabilities and climate change. At the same time, the consensus convention increasingly exposed the G20 to vetoes and lowest-common-denominator outcomes, while intensifying US–China rivalry, Russia’s war against Ukraine and wider geopolitical fragmentation made common positions harder to sustain. Annual rotating presidencies also produced discontinuity and uneven follow-through. The result has been a widening gap between the G20’s representativeness and convening power, on the one hand, and its capacity to convert declarations into durable collective action, on the other (Cooper and Pouliot, 2015; Prime Minister’s Office, 2025).

The UK government now invokes that history in describing the significance of its forthcoming 2027 Presidency (Prime Minister’s Office, 2025). The parallel is instructive, but the nature of the present crossroads is different. In 2009 a common crisis aligned the immediate interests of the major powers. In 2027 the central governance problem is likely to be that interdependence is deepening while political agreement is becoming more difficult. Strategic competition increasingly permeates trade, technology, energy, finance, supply chains and industrial policy, while many global problems require combinations of capabilities that do not correspond to G20 membership.

The institutional choice is therefore whether the G20 continues to treat G20-wide agreement as the principal test of success, or develops an additional capacity to organise effective cooperation when comprehensive agreement is unavailable. The UK’s 2027 Presidency provides an opportunity to initiate the latter path without discarding the advantages of consensus.

2. The Problem: When Consensus Becomes a Constraint

Consensus has important advantages in an informal forum without supranational authority. It protects sovereignty, encourages governments to reveal objections during negotiation and gives common commitments political legitimacy. The problem arises when consensus ceases to be an objective and becomes a prerequisite for collective action.

As the interests, circumstances and domestic constraints of G20 members become more heterogeneous, two failure modes become more likely. Consensus failure occurs when no agreement is reached because one or more members reject it. Lowest-common-denominator failure occurs when agreement is preserved only by reducing substantive ambition. The second can be less visible but equally consequential: institutional continuity is maintained while the resulting commitment is too weak to alter the underlying collective outcome.

The G20 should therefore distinguish between maximising the breadth of assent and maximising effective collective problem-solving. Where the two coincide, consensus is ideal. Where they diverge, the operating architecture should permit cooperation to proceed without imposing obligations on governments that do not participate. Research on climate clubs, regime complexes and minilateral cooperation provides important precedents for this logic (Nordhaus, 2015, 2021; Keohane and Victor, 2011; Eckersley, 2012).

3. From Johannesburg to a Three-Tier Architecture

The 2025 Johannesburg Summit created an important precedent. With the United States absent and opposed to important elements of the South African Presidency’s agenda, and Argentina declining to endorse the Leaders’ Declaration, South Africa nevertheless proceeded on the basis that the declaration commanded overwhelming support among participating members. Contemporary reporting treated this as a significant departure from previous G20 practice (Cocks et al., 2025).

This broad-consensus practice is valuable because it prevents one or a few members from exercising an effective veto while preserving voluntary participation. It should not, however, be confused with majority voting: dissenting governments acquire no obligations. Nor does it solve the deeper problem. On many issues, overwhelming support may be available only for commitments too moderate to be consequential.

The transition to the UK Presidency must also be understood as a transition from the current US Presidency. The United States assumed the 2026 Presidency with a deliberately narrower, results-oriented agenda centred on the G20’s economic and financial core. Its Finance Track priorities include modernising financial regulation, examining excessive global imbalances, improving debt transparency and restructuring, supporting digital assets, improving cross-border payments and financial literacy. More broadly, the US approach has emphasised limiting regulatory burdens, affordable energy and secure supply chains, and technological innovation. This represents a sharp break with the expansive agenda of recent presidencies and reinforces the case for focus, implementation and measurable results.

The UK should neither simply restore the broader pre-2026 agenda nor perpetuate the US narrowing of the G20’s remit. Its three-tier architecture offers a way to reconcile the lessons of both transitions. From South Africa, it would retain the principle that overwhelming support can permit willing members to proceed when unanimity is unavailable, without binding dissenters. From the United States, it would retain the emphasis on selectivity, functional relevance and results. The third tier then adds the missing institutional mechanism: when neither G20-wide consensus nor broad consensus can deliver sufficiently ambitious action, the Presidency can organise a limited set of pivotal powers around a precisely defined problem. In this way, the UK Presidency can bridge the South African and US approaches—preserving inclusiveness where possible, while making focused, problem-solving cooperation possible where it is not.

The UK should therefore propose a three-tier operating architecture for G20 cooperation:

1. Consensus where possible: seek G20-wide agreement whenever sufficiently ambitious common action can command the support of all members.

2. Broad consensus where feasible: where universal agreement is impossible but overwhelming support exists, allow willing members to proceed without imposing obligations on dissenters.

3. Pivotal-power coalitions where necessary: where neither consensus nor broad consensus can generate sufficiently effective action, organise cooperation among the countries whose participation and capabilities are pivotal to solving the problem, while designing the agreement for wider accession and safeguarding the legitimate interests of countries outside the coalition.

The architecture is cumulative rather than substitutive. Each tier is used only when the broader form of agreement cannot produce sufficiently effective action. The decisive question therefore becomes not only ‘How many G20 members support this agreement?’ but also ‘Which countries must cooperate for this agreement to become effective?’

4. Pivotal-Power Coalitions: Matching Participants to Problems

A pivotal power is a country whose participation can materially affect whether a particular collective challenge is successfully addressed. Pivotality is functional and problem-specific, not a permanent geopolitical status. Relevant sources of pivotality include economic scale and market access; technological and scientific capabilities; financial resources; control over critical inputs; production or consumption shares; regulatory authority; geographical position; implementation capacity; and the ability to enable or attract participation by others.

This principle matters because the functional geography of a global problem often differs from the membership geography of the G20. Climate transition may require major emitters, clean-technology producers, financial centres and critical-mineral suppliers. Sovereign-debt restructuring requires the debtor, relevant bilateral and multilateral creditors, private creditors and international financial institutions. AI governance may require jurisdictions possessing frontier capabilities, compute, semiconductors, major markets and regulatory influence. Some pivotal participants will be outside the G20, while some G20 members may have only a limited operational role in a particular agreement.

The proposal is therefore not a fixed club of middle powers or an alternative geopolitical bloc. It is a procedure for assembling the actors required by the problem. Following the spirit of polycentric governance, however, functional effectiveness cannot be the sole criterion of legitimacy. A coalition assembled to solve one collective-action problem should not do so by exporting material social, economic, security or environmental harms to countries outside the coalition. Its recommendations should therefore be assessed for significant adverse cross-border effects on non-participants. Where such harms are reasonably foreseeable, the coalition should seek to prevent them; where harmful activity is occurring, to cease or modify it; and where harm has nevertheless occurred, to repair, restore or otherwise rectify it wherever reasonably feasible. This responsibility is stronger than a simple requirement that outsiders remain legally unbound by the coalition's decisions: non-participation should not become a licence for coalition members to externalise the costs of their cooperation.

This safeguard gives pivotal-power coalitions a substantive criterion of legitimacy: their proposals should remain in the global public interest. That does not imply that every policy must benefit every country, or that any adverse effect creates an absolute veto. Trade-offs are unavoidable. The appropriate standard is one of reasonable feasibility and proportionality: identify significant harms, consider less harmful alternatives, distinguish unavoidable adjustment costs from preventable injury, and adopt effective rectification where the burden imposed on outsiders would otherwise be disproportionate to the global benefit sought. Affected non-participating countries should have a transparent opportunity to raise concerns and present evidence before recommendations are finalised.

5. The G20’s New Operating Role: Identify → Convene → Enable → Monitor → Demonstrate → Expand

The operating sequence in this section applies specifically to the third tier of the proposed architecture: pivotal-power coalitions. It is not intended to govern ordinary G20-wide consensus or broad-consensus agreements. Its purpose is to provide a practical template for the Presidency when it must assemble, support and expand a problem-specific coalition because the first two tiers cannot generate sufficiently effective action. At each stage, the coalition should also test whether its proposed action remains in the global public interest by considering material effects on non-participating countries and the feasibility of preventing or rectifying adverse spillovers.

Identify. Define the collective-action problem, its principal cross-border externalities and complementarities, the capabilities required for progress, and the countries and institutions that possess them. The diagnosis should include material social, economic, security and environmental effects that proposed coalition action could impose on countries outside the coalition.

Convene. Use the Presidency’s political authority to bring the relevant pivotal powers – including non-G20 countries – into a problem-specific negotiation with a clear mandate and timetable.

Enable. Mobilise international organisations, development banks, standard-setting bodies, businesses and scientific communities to supply analysis, finance, standards, implementation capacity and institutional support.

Monitor. Translate political commitments into measurable objectives, transparent reporting and review mechanisms appropriate to the issue. Monitoring should cover not only progress toward the coalition's objectives but also significant adverse spillovers on non-participants and the implementation of agreed measures to prevent, cease, repair, restore or otherwise rectify them.

Demonstrate. Generate evidence that cooperation produces benefits for participants, contributes materially to addressing the global problem and does not achieve those gains by exporting material harms to outsiders. Where adverse effects arise, demonstrate that reasonable steps have been taken to prevent, cease, repair, restore or otherwise rectify them. Such evidence is essential both to the coalition's legitimacy and to making later participation attractive.

Expand. Build transparent accession provisions into the agreement from the outset, so that countries initially unable or unwilling to participate can join when their interests and capacities permit.

This is orchestration rather than hierarchy. The G20 would not acquire supranational powers or a large bureaucracy. It would use its existing convening authority to mobilise actors and institutions possessing capabilities that the G20 itself lacks – a role for which there is already precedent in international financial governance (Abbott et al., 2015; Viola, 2015).

6. Open Accession: Coalitions as Pathways to Wider Cooperation

The principal political risk of coalition-centred cooperation is that it could produce closed clubs, discriminatory standards or rival blocs. The answer is to make openness to subsequent accession a constitutive feature rather than an afterthought.

A G20-supported pivotal-power coalition should therefore satisfy six minimum design conditions: (i) transparent participation criteria; (ii) non-discriminatory accession for countries able to meet the commitments; (iii) compatibility, where possible, with wider multilateral rules and institutions; (iv) capacity-building or transitional arrangements for prospective entrants; (v) periodic review of both membership conditions and substantive commitments; and (vi) a global-public-interest safeguard requiring assessment of material social, economic, security and environmental harms to non-participating countries and, wherever reasonably feasible, measures to prevent, cease, repair, restore or otherwise rectify such harms. Open plurilateral arrangements can complement wider multilateral institutions when their design facilitates expansion rather than exclusion (Hoekman and Sabel, 2019).

The relevant test of success is consequently dynamic and external as well as internal. A coalition should be judged not only by what its initial members agree and whether it attracts wider participation, but also by whether it solves the targeted problem without materially worsening other dimensions of global welfare or transferring significant costs to outsiders. Open accession and the global-public-interest safeguard are therefore complementary: the first prevents unnecessary exclusion; the second protects countries that remain outside the coalition.

7. International Organisations as the Institutional Backbone

Coalition-centred G20 governance should work through, not around, existing international organisations. The G20’s comparative advantage is high-level political convening. Technical analysis, finance, standards, monitoring and implementation capacity already reside in organisations such as the IMF, World Bank, WTO, OECD, Financial Stability Board, UN agencies and regional development banks.

The G20 Mutual Assessment Process offers a useful precedent. Following the Pittsburgh Summit, the G20 asked the IMF to assess whether national and regional policy frameworks were collectively consistent with strong, sustainable and balanced growth, drawing on the expertise of other international bodies (IMF, 2009). The broader lesson is institutional: the G20 can define political objectives and organise cooperation while relying on specialised organisations for technical and operational functions.

For pivotal-power coalitions, the division of labour should be explicit: the G20 Presidency provides political convening and strategic direction; coalition participants negotiate and implement commitments; relevant international organisations provide analysis, finance, standards and monitoring; and domestic governments remain responsible for implementation. Where appropriate, international organisations should also help assess cross-border spillovers, give affected non-participating countries channels to present evidence and concerns, and evaluate whether proposed prevention or rectification measures are feasible and proportionate. This makes the proposal feasible without constructing another permanent international bureaucracy.

8. Why the UK Is Well Placed to Lead in 2027

The value of a G20 Presidency lies not only in selecting agenda items but in shaping the process through which cooperation takes place. A UK initiative to establish a recognised pathway for pivotal-power coalitions would therefore constitute institutional entrepreneurship rather than the assertion of British substantive preferences across every policy domain.

The historical parallel with 2009 is useful. The UK did not possess the national resources to resolve the global financial crisis. Its contribution lay in helping organise a collective response among the countries and institutions that possessed the necessary capabilities. In 2027 it can play an analogous role under different conditions: instead of organising a common response to one acute crisis, it can establish procedures for organising differentiated cooperation across a portfolio of chronic collective-action problems.

This model is particularly compatible with the UK’s sources of international influence: diplomatic convening power, financial expertise, regulatory and standard-setting capabilities, links with international financial institutions, relationships with European and Commonwealth partners, and the depth of London’s financial markets. UK leadership would be enabling rather than exclusive: its contribution would be to establish a process through which the relevant actors can cooperate and successful cooperation can widen.

9. Applying the Model to Emerging UK 2027 Priorities

Secure and resilient global growth and financial stability. HM Treasury has stated that the UK will use the 2027 Presidency to promote secure and resilient global growth, including through the global financial system (HM Treasury, 2026). Coalition pathways could focus on concrete vulnerabilities – payment-system resilience, cross-border financial risks, illicit finance or capital-market fragmentation – by convening the jurisdictions and institutions whose actions are systemically consequential.

Sovereign debt and development finance. The UK has linked its Presidency to reform of the international debt architecture and a stronger voice for African borrowers (FCDO, 2025). Debt restructuring is inherently constellation-specific: the relevant debtor, bilateral creditors, multilateral lenders and private creditors must cooperate. Development-finance coalitions could similarly assemble donor governments, multilateral development banks, recipient countries, institutional investors and financial centres around investable country or sector platforms (FCDO, 2026a; House of Commons Library, 2026).

Fair trade, investment and resilient supply chains. Growth and opportunity, stable growth, fair trade and investment have been placed at the centre of the UK-hosted G20 (Prime Minister’s Office, 2025). Coalitions could develop interoperable standards, investment frameworks or supply-chain arrangements among pivotal producers, consumers and trading hubs, with accession open to additional economies.

Climate and clean energy. The UK is seeking stronger international leadership on climate and clean energy and greater mobilisation of public and private climate finance (FCDO, 2026a; UK Special Representative for Climate, 2026). Rather than attempt one comprehensive G20 bargain, the Presidency could use the coalition pathway for specific bottlenecks such as grids, storage, methane, clean shipping, green industrial standards or critical minerals.

Digital development and artificial intelligence. The UK’s Digital Development Strategy envisages carrying a robust digital-development agenda through the US and UK G20 Presidencies in 2026 and 2027 (HM Government, 2024). AI governance is particularly suited to a pivotal-power approach because frontier capabilities, compute, semiconductors, major digital markets and regulatory influence are concentrated in a limited number of jurisdictions. Open coalition agreements could promote interoperability while preserving a route to wider participation.

10. Political Feasibility: Why G20 Members Could Accept the Reform

The proposal is deliberately evolutionary. It does not require amendment of a treaty, because the G20 has no constitutive treaty; it does not create formal majority voting; it does not authorise coalitions to bind non-participants; and it does not displace the mandates of existing international organisations. It establishes an additional pathway for voluntary cooperation under the political umbrella of the G20.

The principal objection – that coalitions may fragment the international order or impose costs on those excluded from their decisions – is addressed by open accession, transparency, compatibility requirements and the global-public-interest safeguard. Coalition members would remain free to undertake ambitious voluntary cooperation, but G20 sponsorship would carry a corresponding expectation that they consider material harms to outsiders and prevent, cease, repair, restore or otherwise rectify them wherever reasonably feasible. The reform therefore changes the G20’s practice more than its formal structure. That is precisely why a Presidency can initiate it.

The principal objection – that coalitions may fragment the international order – is addressed by open accession, transparency and compatibility requirements. The reform therefore changes the G20’s practice more than its formal structure. That is precisely why a Presidency can initiate it.

11. A Practical UK Roadmap for 2026–2028

Before the Presidency: build support and select pilots

During 2026 and the transition into the Presidency, the UK should consult the incoming and outgoing Troika members, major G20 partners, relevant non-G20 countries and international organisations on the three-tier architecture. It should identify two or three issues on which a pivotal-power coalition could generate a visible gain within a realistic timetable. Selection should be based on functional necessity, political feasibility, measurable outcomes, scope for subsequent accession and the capacity to avoid or rectify material adverse spillovers on non-participants – not on a desire to create a UK-branded initiative in every priority area.

During 2027: establish the pathway and launch demonstration coalitions

At the outset of the Presidency, the UK should seek political recognition that G20 cooperation can legitimately take three forms: consensus, broad consensus and voluntary pivotal-power coalitions. For each pilot, the Presidency should publish or circulate a short coalition mandate identifying the problem, required capabilities, initial participants, relevant international organisations, measurable objectives, accession conditions, foreseeable material effects on non-participants and procedures for preventing or rectifying adverse spillovers wherever reasonably feasible. The coalitions should be integrated into existing Finance and Sherpa Track processes where appropriate rather than creating parallel bureaucracies.

At the 2027 Leaders’ Summit: institutionalise the operating doctrine

The Leaders’ Summit should aim to endorse the principle that problem-specific coalitions may be convened under G20 auspices when G20-wide agreement is unavailable, provided that participation is voluntary, dissenters incur no obligations, accession conditions are transparent, relevant international institutions are engaged, and coalition proposals are subject to a global-public-interest safeguard concerning material social, economic, security and environmental harms to non-participants. The objective is not to secure endorsement of every coalition outcome by every G20 member, but to secure recognition of the coalition pathway itself – including its responsibilities toward outsiders – as legitimate G20 practice.

After the Presidency: create continuity without bureaucracy

The UK should work with the Troika and relevant international organisations to ensure that successful coalitions continue beyond 2027. A light continuity mechanism should record mandates, commitments, monitoring arrangements and accession requests. Responsibility for technical follow-through should sit principally with the institutions already possessing the relevant expertise. This would allow the UK Presidency to leave a repeatable operating practice rather than a portfolio of initiatives dependent on continued British chairmanship.

12. Recommendations for the UK 2027 G20 Presidency

1. Retain consensus as the preferred basis for G20-wide commitments, while making clear that consensus is not a prerequisite for all collective action.

2. Consolidate the broad-consensus practice: where overwhelming support exists, willing members may proceed without imposing obligations on dissenters.

3. Establish a recognised G20 pathway for problem-specific pivotal-power coalitions involving both G20 and non-G20 countries.

4. Require each coalition to specify the collective-action problem, capabilities required, pivotal participants, measurable objectives, implementation responsibilities, relevant international organisations, and foreseeable material effects on non-participating countries.

5. For third-tier pivotal-power coalitions, adopt the operating sequence Identify → Convene → Enable → Monitor → Demonstrate → Expand as a practical template for coalition support.

6. Make open accession mandatory for G20-supported coalitions through transparent entry criteria, non-discrimination, compatibility provisions, capacity-building where appropriate and periodic review; and require a global-public-interest safeguard under which material social, economic, security or environmental harms to non-participants are prevented, ceased, repaired, restored or otherwise rectified wherever reasonably feasible.

7. Pilot the approach in only two or three areas where the UK’s emerging priorities coincide with a strong functional case for coalition action.

8. Use existing international organisations as the technical and operational backbone rather than creating a substantial new G20 bureaucracy.

9. Seek Leaders’ recognition of the coalition pathway itself as a legitimate form of G20 cooperation, even where not every member participates in a particular coalition.

10. Measure the 2027 legacy partly by collective action generated: commitments implemented, resources mobilised, measurable outcomes achieved, harms to non-participants avoided or rectified, additional countries acceding and successful coalitions continuing under subsequent Presidencies.

13. How This Could Revive the G20

The G20’s institutional problem is not simply that geopolitical disagreement makes communiqués harder to negotiate. It is that a forum created to mobilise collective action risks being judged primarily by its ability to negotiate language acceptable to all members. As disagreement increases, this can create a cycle in which more diplomatic effort produces less substantive action.

The three-tier architecture would reconnect G20 diplomacy to observable problem-solving. Consensus would continue to supply legitimacy where common commitments are possible. Broad consensus would prevent isolated opposition from blocking willing members. Pivotal-power coalitions would permit ambitious action where the relevant participants form a smaller or differently constituted group. Open accession would create a mechanism through which initially limited cooperation can widen, while the global-public-interest safeguard would ensure that greater freedom for smaller groups is accompanied by responsibility toward countries outside them.

This would revive the G20 in four linked senses. It would restore effectiveness by allowing action when universal agreement is unavailable; restore relevance by matching participation to the functional requirements of each problem; restore adaptability by permitting different configurations of cooperation across different issues; and restore institutional purpose by making the G20 a platform that generates, supports and expands collective action while requiring G20-sponsored coalitions to remain attentive to their wider global consequences.

Such a role is well suited to the G20’s informal character. The reform does not ask the G20 to become a world government. It asks it to become better at the function for which its political composition gives it a comparative advantage: organising cooperation among actors with the capacity to change global outcomes.

14. Conclusion: A 2027 Institutional Legacy

In 2009 the United Kingdom hosted the G20 when a global crisis forced governments to recognise that national action alone was inadequate. The London Summit helped establish the G20 as a central institution of international economic cooperation because it connected political leadership with concrete collective action.

In 2027 the G20 again stands at a crossroads. The challenge is no longer simply to coordinate the world’s major economies in response to a common financial emergency. It is to sustain effective cooperation when the major powers increasingly disagree about priorities, rules and the distribution of costs.

The wrong response would be to abandon consensus. The equally wrong response would be to allow the search for consensus to determine the limits of global problem-solving. The UK should instead promote a simple operating doctrine: seek consensus where possible; use broad consensus where feasible; build pivotal-power coalitions where necessary; design those coalitions to expand; and require them to pursue their objectives without externalising material social, economic, security or environmental harms onto countries outside them.

If the UK can establish this doctrine as a legitimate and repeatable G20 practice, the Presidency would have a legacy extending beyond any single priority or communiqué. As in 2009, UK leadership would consist principally in organising the international conditions under which collective solutions become possible. The result could be a G20 better suited to a fragmented world: an institution capable not merely of recording disagreement, but of building practical coalitions through which cooperation can begin, demonstrate its value and widen over time – while ensuring that the freedom to act in smaller groups remains bounded by responsibility to the wider international community.

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