By Paul Reynolds
World Affairs correspondent, BBC News website
Given its current policies, the British government is left with few options in the aftermath of the London bombings.
The contrast with the political impact of the Madrid attacks of a year ago, which killed 191 people, is significant.
The attacks brought London's transport network to its knees
In Spain, three days after the bombs, voters voted out Jose Maria Aznar, who had supported the invasion of Iraq, and voted in Jose Luis Rodriguez Zapatero, who did not.
In Britain, voters took a decision in the recent general election to keep Tony Blair in power, not, it is reckoned, because of Iraq, but despite Iraq.
It could be said that if al-Qaeda or one of its loosely affiliated groups was behind the London attacks, then this was al-Qaeda's response to that election.
The timing appears to have been connected to the G8 summit - but that is tactics. The strategy is what really counts, and the strategy appears to be aimed at punishing Britain and trying to get it to change its own policies.
That will not happen under Mr Blair.
He said so immediately after the attacks, and while politicians often say such things following outrages, there is not much reason to doubt Tony Blair's determination.
He is committed to staying in Iraq and to the hope that, in due course, the insurgency there can be overcome and Iraq will develop into a functioning, democratic state backed by its oil riches.
He, like US President George W Bush, proclaims this as a vital struggle in the modern age.
Tony Blair is not a politician who regularly changes his mind
Britain therefore remains in the front line, and the option of withdrawing from Iraq and minimising the risk of further attacks is not presently open to British voters.
They have taken their decision and must accept the consequences.
It is possible that things could change when Mr Blair steps down, but there is no sign that any successor would undertake the kind of policy switch seen in Spain and withdraw the troops from Iraq.
And it is possible that public unease over Iraq could in due course bubble up through the system to effect a change in policy. But that is some way off.
This trend, if it develops, will be a key one to watch.
It is often the case in the confrontation between governments and groups using political violence that governments, if put under enough pressure, make concessions.
The British government policy towards the IRA has changed hugely over the years as both sides fought each other to a standstill.
Even the Israelis are withdrawing from Gaza - not because they want to, but because they feel they have to.
There are those who argue that it does not matter what Western governments do these days, that they are all under threat and some will come under attack.
However, that discounts the level of political thinking which is evident among al-Qaeda groups. They certainly have their political strategy and judge governments accordingly.
Londoners quickly returned to some kind of normality
Al-Qaeda might not have a detailed political manifesto but it does have aims.
The London bombings seem to signal, too, a failure of the British government's hope that it could divert attention from Iraq by concentrating, for example, on helping the Palestinians achieve an independent state.
In January this year, a conference was held in London to examine how the Palestinians might be supported.
The meeting was partly designed to deflect Arab opinion away from the belief that Britain was only following a US agenda in the Middle East.
It might have had some effect among moderate opinion.
It appears to have had none among the extremists.