Gordon Brown and his fellow G20 leaders put together a package of measures which they claimed amounted to more than $1tn (£748bn) of new resources to be injected into the moribund global economy, and a radical clean-up of financial markets.
"We start from the belief that prosperity is indivisible; that growth, to be sustained, has to be shared; and that our global plan for recovery must have at its heart the needs and jobs of hard-working families, not just in developing countries but in emerging markets and the poorest countries of the world too; and must reflect the interests, not just of today's population, but of future generations too," they said in their communique. "Together with the measures we have each taken nationally, this constitutes a global plan for recovery on an unprecedented scale."
Here are the key measures.
Reforming the world's banking system
City firms will face a new super-regulator. The Basel-based Financial Stability Forum, which was set up a decade ago as an informal network of central banks, finance ministries and market regulators, will be renamed the Financial Stability Board, and given sweeping new powers to oversee banks and international markets. The G20 promised to create a "stronger, more globally consistent, supervisory and regulatory framework for the future financial sector, which will support sustainable global growth and serve the needs of business and citizens."
The FSF immediately made its intentions clear by issuing a series of edicts:
• Bankers' pay and bonuses must reflect the risks they are taking - so huge cash bonuses for high-risk bets are out.
• Hedge funds must disclose their leverage levels - effectively how indebted they are - so regulators can assess the risks they are taking.
• Accounting rules will be radically rewritten to end the practice of "mark to market" valuations, which exacerbated the crash by forcing banks to keep slashing the value of their toxic assets.
• Credit derivatives, the complex bets that sent the Lehman Brothers collapse ricocheting through the world's markets, can no longer be sold "over the counter" between one financial institution and another - instead, there will have to be a central clearing house, so the trades can be carefully controlled.
• Credit ratings agencies, which gave many of the toxic assets at the heart of the crisis AAA ratings, will be more closely supervised.
• The FSF will collaborate with the International Monetary Fund to spot looming economic and financial crises at an early stage.
The G20 also announced a dramatic crackdown on tax havens.
Cleaning up the banks
Most major economies have been wrestling with the challenge of rescuing failing banks and removing billions of dollars of dodgy assets from their balance sheets. Barack Obama's treasury spokesman, Tim Geithner, has struggled to convince the markets that Washington's plans will work. But Brown said the G20 leaders had agreed a common global approach and promised to take "aggressive action" to patch up banks' balance sheets, and help them unblock lending to families and firms. The Japanese prime minister, Taro Aso, had pressed his fellow leaders to act fast to clear up toxic assets, or face a "lost decade" like that suffered by his country in the 1990s.
The G20 said international rules on banks' capital will also be radically rewritten, forcing them to hold more reserves in good times so that they are less exposed in future crises.
Restoring growth to the global economy
Despite failing to persuade his fellow leaders to sign up to fresh stimulus measures, Brown said the world was in the midst of "an unprecedented fiscal expansion". The G20 countries totted up the fiscal stimulus measures they had already agreed to take, which they said would amount to a total of $5tn by the end of 2010 - and promised to "do whatever is necessary" to nurse the world economy back to health and create or safeguard millions of jobs.
Central banks will keep interest rates at rock bottom levels for as long as is necessary to restore growth.
The International Monetary Fund's resources will be trebled to $750bn.
Special Drawing Rights - the mechanism that gives IMF members the right to borrow from each other's foreign currency reserves - will be increased for the first time since 1980, to $250bn, more than 10 times the current level. The G20 hopes the ability to borrow will give struggling economies more confidence and prevent them being picked off by financial markets.
Other multilateral development banks, such as the Asian Development Bank, will be given a further $100bn.
The G20 asked the IMF to monitor the success of these policies and let them know whether more is needed; they will meet in New York in the autumn for a progress report. But Brown said these measures would bring recovery to the world economy faster than would otherwise have been possible.
Strengthening international institutions
Brown declared the death of the "Washington Consensus" of financial market liberalisation, privatisation and unfettered capitalism promulgated by the Bretton Woods institutions - the IMF and the World Bank. The IMF will be asked to take a stronger role in supervising the world financial system.
The bank and the fund will be modernised to give a bigger role to developing countries, and fit them for the challenges of the 21st century global economy: "in order for our financial institutions to help manage the crisis and prevent future crises we must strengthen their longer term relevance, effectiveness and legitimacy".
The IMF has been asked to accelerate its ongoing review of "quota and voice" - the representation of poor countries in its decision-making - and come up with reforms by 2011.
In future the heads of the bank and the fund will be chosen "on merit", instead of the current stitch-up which guarantees the fund job to a European and the bank to an American.
Boosting international trade
G20 leaders promised a total of $250bn, made up partly of private contributions as well as government money, to help finance international trade deals which have ground to a halt as firms in poor countries struggle to borrow from dried-up credit markets.
Brown said they had extended until the end of 2010 the pledge they made in Washington in November to avoid throwing up new protectionist barriers. They asked the World Trade Organisation to report quarterly and "name and shame" countries that fail to comply with this pledge. Those countries will then be asked to rectify their polices immediately. The World Bank recently reported that 17 of the countries in the G20 had increased trade barriers since the November summit.
They repeated their pledge to conclude the Doha round of WTO talks, launched in 2001; but there was no repeat of the deadline mooted in Washington for negotiations to be concluded. An attempt will be made to relaunch the round at the G8 summit in Sardinia in July.
Ensuring a fair and sustainable recovery for all
They promised "not only to restore growth but to lay the foundation for a fair and sustainable world economy".
The G20 countries reaffirmed their commitment to meeting the Millennium Development Goals and hitting their Gleneagles aid commitments to double aid to the world's poorest countries by 2010. In total, they said their measures would provide an extra $50bn to the pool, including $6bn to be raised from IMF gold sales, new contributions to the World Bank's "vulnerability fund", and $19bn of the new IMF Special Drawing Rights, which will be allocated to low-income countries.
Back at home, they pledged to "support employment by stimulating growth, investing in education and training, and through active labour market policies, focusing on the most vulnerable".
They also promised to push for a tough new climate deal at the Copenhagen Summit in December.
Five things we learned
1 The emergence of G2 While everyone was still trying to find a way to remember all 20 nations of the global elite, the US and China quietly emerged as the new elite partnership.
2 The development lobby proved far stronger than the environmental lobby There was much more emphasis, and hard cash, given to development than a low-carbon recovery.
3 The IMF is back An institution that was cash-strapped and in danger of irrelevance only a year ago is now stronger than ever. Whether it will be successfully reformed as promised is still an open question.
4 Another special relationship survives Obama held a bilateral session with Saudi King Abdullah. Oil prices, faltering Middle East peace efforts, and maybe a veiled discussion about the king's recent shake-up in succession plans were on the agenda.
5 Obama needs an off switch The age of oratory is back, but we learned that you can get too much of a good thing, especially if you try to sit through his hour-long press conferences.
