By Steve Schifferes
BBC News economics reporter at the G8 summit in Gleneagles
Thursday was a day of sad and dramatic images at the G8 summit at Gleneagles in Scotland.
Bush and Blair were due to talk about climate change and aid
Politicians, police and journalists watched the horrific events unfolding in London, huddled around the giant television screens dotted around the conference centre.
The leaders of the world's eight most powerful nations, gathered together, were quick to show their solidarity with Britain as they stood side-by-side behind Prime Minister Tony Blair as he condemned the attacks.
"We will prevail, and they will not," Mr Blair told the nation, before leaving the conference by helicopter to see the situation in London for himself.
But as Mr Blair left the crucial negotiations on climate change, the question arose of whether the central objective of the attack was to disrupt the summit - and whether in fact, it has at least partly succeeded.
Mr Blair's sudden departure also disrupted plans for a dialogue with five of the most important developing countries - India, China, Brazil, South Africa and Mexico.
Their leaders had been invited to the summit to discuss climate change and trade negotiations, in which they are playing an increasingly important role.
But the prime minister already had the outlines of a climate change deal before the bombs struck, appearing with US President George W Bush in an early morning press conference to announce that the US would support some sort of language accepting that human activity was causing global warming.
Media attentions have turned elsewhere
It was not enough for many environmental groups, but it did earn the endorsement of French President Jacques Chirac, who earlier had been threatening to demand a separate statement all G8 countries except the US.
As negotiations continued throughout the afternoon, chaired by Foreign Secretary Jack Straw, it became clear that any announcement on climate change would have to postponed until the last day of summit.
Mr Blair was determined to return to Gleneagles overnight in order to greet African leaders who have been invited to the summit to endorse the other big deal of this summit - a pledge by rich countries to double their aid to Africa.
Again, the heart of this deal was sealed last week, when President Bush announced that the US would be joining the EU in pledging more money to Africa - increasing aid by $25bn (£14.2bn) by 2010.
This is less money than the development campaigners want - and some of it may have already been pledged - but it nevertheless represents a triumph for the mass mobilisation of the Make Poverty History campaign.
The bomb attacks in London, however, inevitably will take some of the momentum out of that campaign, which culminated in a triumphant Live 8 concert in Edinburgh on Wednesday night.
While the obvious desire for everyone to pull together has, in some ways, made it easier to agree a deal on contentious issues such as climate change, it has also made it harder for campaigners to criticise those deals for not going far enough.
It is not clear whether the summit will regain its momentum
For Tony Blair, aid to Africa was always a central part of the war on terror - to be used to persuade people in developing countries that the West offers them hope.
It is a strategy he has worked hard at persuading Mr Bush to endorse, and in some ways this was the central purpose of the Gleneagles summit.
Mr Blair is determined to demonstrate that commitment remains intact, and to bring the summit to a successful conclusion.
He cannot change the fact that much of the world media attention is now focused on the horrific events in London rather than the deals he has pushed so hard for in Scotland.
But he will be hoping that the message of hope delivered by the summit will, in the long run, outweigh the voices of terror.