The negotiations: Huddles with heads of state pay off as Brown gets his deal

Sarkozy, Obama and an England shirt signed by David Beckham all played a crucial role at the G20 summit

Much of the real work at the G20 summit was done in this "leader's lounge", complete with white and pea-green sofas and artificial trees shipped in to soften the look of the ExCeL centre in London's Docklands, which officials described as "a series of aircraft carriers" and a "Star Wars set".

If it looked like an austerity summit, Gordon Brown didn't mind. It would not have looked good for leaders of the richest nations to discuss the biggest economic crisis since the 1930s at a swanky hotel or royal palace, where they have often gathered in the past.

Failure was never likely, despite a hitch on the eve of the summit, when M. Sarkozy and Mrs Merkel took the unusual step of holding a joint press conference at a Knightsbridge hotel to demand tougher new rules for the financial system.

Although M. Sarkozy's language was explosive, he and Mrs Merkel concentrated most of their fire on financial regulation rather than the desire of President Obama and Mr Brown for a further fiscal stimulus.

M. Sarkozy's appearances can be deceptive. British officials said that, despite his headline-grabbing pre-emptive strike for domestic purposes, he played a constructive role.

Yesterday he took Mirek Topolanek, the Czech Prime Minister, to one side and upbraided him for attacking President Obama's call for a further fiscal stimulus as the "road to hell". There was much finger-pointing as the French President apparently accused Mr Topolanek, whose country holds the European Union's rotating presidency, of not speaking for the whole of Europe. There may be some tension in the air when Mr Topolanek plays host to President Obama at an EU-US summit in Prague on Sunday.

By the time the 20 leaders arrived at the ExCeL from 7.30am yesterday, a deal was in sight. After the Franco-German putsch, differences among the 20 over how far and fast to go on regulating the banks were narrowed over a working dinner at Downing Street on Wednesday. The leaders, joined by their wives for coffee, did not leave until 11pm.

Mr Brown was confident enough of agreement to retire to bed at about 11.30. He was back at his desk by 6am. By then, the British "sherpas", officials tasked with mapping out a route for leaders at such events, had worked through the night on drafting and redrafting the final communiqué. Led by Jon Cunliffe, Mr Brown's adviser on Europe and international financial affairs, they were based at Church House, Westminster, and were passed notes containing the latest intelligence from the dinner as it progressed.

The main problem, according to British officials, was not a transatlantic rift over a fiscal stimulus or American opposition to tough banking rules, but doubts among emerging economies, led by China, about the interference in their affairs the new regulatory system would bring.

There was still work to be done during breakfast yesterday. Mr Brown worked the room, ensuring his guests remained "on message" with what had been agreed over dinner.

The formal session then began in a windowless oval "red zone" room, with access strictly limited to VIPs. During breaks, the 20 retreated to the "leader's lounge" without their officials.

The Prime Minister opened by highlighting the dangers of retreating into protectionism. He then took the chair as the leaders worked through every detail of the proposed communiqué, the latest draft displayed on a computer screen in front of each delegation.

"By and large people agreed on the diagnosis of the problem, but the nature of the remedy still had to be negotiated," said one British official.

As news began to leak out about the final package, it was clear by mid-morning that the Prime Minister would not be disappointed. His desire for a new fiscal stimulus closed off by European opposition, Mr Brown looked elsewhere for his "plan for economic recovery and reform". No doubt with a headline in mind, he put together a $1trn package of loans and guarantees through beefed-up bodies such as the International Monetary Fund and World Trade Organisation to ensure the global economy pulls out of recession as quickly as possible.

Although Mr Brown was immersed in a game of "20-dimensional chess", there were some lighter moments. Just before yesterday's roast beef lunch, he pulled a rabbit from the hat – an England football shirt signed by David Beckham. Other leaders looked on enviously as he handed it to a delighted Luiz Inácio Lula da Silva, the Brazilian President. All part of the lobbying for England to host the 2018 World Cup.

Although Mr Brown can count the summit a success, the real star was perhaps President Obama on his international debut. "Incredibly impressive. He quickly established himself as a big player," was one verdict. The queue to get into his press conference last night was longer than that for Mr Brown's.

With the financial markets watching, no leader wanted to be cast as a summit wrecker. "There was a lot of hard work. It wasn't easy," said one British source. "Everyone knew how important it was to be united. A breakdown would have been unthinkable."