Geldof was joined at a rainswept Gleneagles by Bono, of U2, Richard Curtis, the actor Djaimon Honsu and, in a late addition to the Live8 line-up, the actor George Clooney, whom Geldof hailed for being “incredible in America in bringing Left and Right together” on the issues that will confront the world’s most powerful men over the next 36 hours.

President Bush, who met the Gleneagles’ celebrity contingent minutes after arriving by helicopter from Prestwick airport, was “bullish”, Geldof said. “He has in his back pocket what he says is a great American commitment to halving the number of deaths from malaria in Africa.”

Geldof also welcomed an American initiative to promote girls’ education across the continent and held out hope of a breakthrough on lifting the trade tariffs that bar access to Western markets for African countries without their own bilateral trade deals.

Live8 had no time for the violent protesters blocking roads, smashing windows and attacking police, and contrasted them with the “positive” march on Edinburgh at the weekend. “You’ve seen both types of protest,” Bono said. “I’d like to think that our way is better — but we don’t know that. We’ve got a couple of days to find out.”

Earlier, the self-appointed champions of Africa’s poor were greeted by an exhausted but elated Tony Blair four hours after London’s triumph in the Olympic race and three hours before the dinner, hosted by the Queen, at which the challenge for Andrew Fairlie, Gleneagles’ French-trained head chef, was to pre-empt any French criticism of Scottish cuisine.

Mr Blair held out hope of a breakthrough deal on climate change, as well as Africa. The Prime Minister, who said that Britain had long accepted that America would not sign up to the Kyoto treaty on global warming, said that if there was a disagreement it had to be openly acknowledged. But if they did not get an agreement that involved America there would not be an agreement that worked. That was “practical politics”. He added that it was far too easy to “point the finger at America”. China and India would be major producers over the next few years, and unless they were involved in an agreement it would never happen.

Mr Blair and Mr Bush are concentrating on securing agreement around a comprehensive action plan for dealing with the consequences of global warming without labouring disputes about the scientific reasons for it.

Today’s meetings will focus on the climate change issue. Mr Bush, speaking yesterday morning in Copenhagen, acknowledged that the Earth’s surface was warming and that carbon emissions were at least partly to blame. His remarks were welcomed by environmental groups attending the summit as evidence of a new flexibility, but James Connaughton, head of the White House Council on Environmental Quality, told The Times that “ lots of research is still needed” to produce realistic projections of the impact of carbon emissions on future climate change, adding that “much of the modelling so far has been based on hypothetical scenarios. We need more data from the ground.”

African leaders will attend tomorrow’s G8 meetings to press their case for debt relief, more aid, and an easing of trade barriers. Mr Blair saw “hard pounding ahead”, Geldof related after their meeting. He called this “a highly unusual G8” in that it opened with everything still to play for. “The leaders are playing the highest poker but we must remind them they are playing with the lives of those who will go to bed hungry tonight in Africa.”

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