Arguably the most important catalytic effect of the ‘Great Recession’ of 2008–2009 has been the creation of the G20 at the leaders’ level. As a form of improvised diplomacy the G20 merits extensive scrutiny, revealing as it does the degree of adaptation possible in the international system. The G20 links a significant ideational component, a new dynamic between established and emerging powers, and a complex set of issues. The innovative quality of the G20, however, rests on two very distinct strands of activity and tests of accomplishments. The G20 can be viewed as a ‘recession-buster’ with a vital but momentary purpose. Alternatively, the G20 can be taken to be an embedded ‘steering committee’ for the world. Both of these interpretations have validity. The crisis committee scenario highlights a technical regulatory-driven agenda. The steering committee scenario by way of contrast showcases the connection between the G20 and a new type of global settlement. Passing the test as a crisis committee hinges on very specific deliverables. Passing the test as a steering committee is even more demanding as any move toward a new state-specific ‘concert’ is highly contested. This article examines these debates, locating the G20 in a historical/comparative perspective and in terms of the wider context of shifting power structure at the beginning of the twenty-first century.