Group of Twenty (G20) summits in 2009 occurred during the period of maximum reformist zeal, underpinned by a clear policy consensus and policy narrative, the political capital of the G20 leaders, and technical backing of the central banking epistemic community. The summits marked a reassertion of state power by the core and emerging-country G20 leaders over financial markets and firms. This phase in crisis response and reform unfolded during the leadership of the UK and the US The immediate financial crisis morphed into a real economic threat, and with global economic output slumping, a series of major stimulus moves were announced. These joint and several fiscal stimulus and financial rescue measures saw states working via the G20. Crucially this period also resulted in the recognition of the G20 as the principal forum for international economic and financial diplomacy, the creation of the Financial Stability Board (FSB) and enumeration of a series of key regulatory reforms by the G20 leaders, prompted by the assertive central banking technocratic epistemic community, which would constitute elements of the post-crisis global financial regulatory architecture.