Political reaction: Prime Minister Tony Blair has promised "intense police and security service action" to bring those responsible for yesterday's terror attacks to justice.
And he has vowed that the British people will not be intimidated, changed or divided by the bombings, which he described as "an attack not on one nation but on all nations and civilised people".
The prime minister was speaking after leaving the G8 summit at Gleneagles in Scotland to chair a meeting of the cabinet's "Cobra" emergency committee in London.
And he echoed the "sympathy and sorrow" reflected earlier in Queen Elizabeth's open message on behalf of the nation to those affected and to the relatives of those who had been killed and injured.
Opposition leaders Michael Howard and Charles Kennedy closed ranks behind the government's defiant response to the bombers, while the Archbishop of Canterbury Rowan Williams joined Muslim leaders in a show of "solidarity and common purpose".
At the same time Mr Blair welcomed the determination of his fellow G8 leaders that an attack which paralysed London would not be allowed to derail the Gleneagles summit on African poverty and climate change.
As world leaders joined the condemnation of the bombings, Mr Blair expressly welcomed the statement by the Muslim Council of Britain, declaring: "These evil deeds make victims of us all. The evil people who planned and carried out this series of explosions in London want to demoralise us as a nation and divide us as a people. All of us must unite in helping the police to capture these murderers."
As after the September 11th attacks on the US, one of Mr Blair's immediate and pressing concerns was that the long-predicted "inevitable" terrorist attack should not sour community relations in multicultural Britain. "We know that these people act in the name of Islam," he said. "But we also know that the vast and overwhelming majority of Muslims here and abroad are decent and law-abiding people who abhor those who do this every bit as much as we do."
Paying tribute "to the stoicism and resilience of the people of London", Mr Blair said he had been briefed by all relevant ministers and officials about the measures under way to restore transport and other public services to the capital.
Having also heard from all the security and intelligence chiefs at the Cobra meeting, Mr Blair promised: "There will of course now be the most intense police and security service action to make sure that we bring those responsible to justice."
However, while that was the immediate priority for MI5, MI6, Special Branch and the Met's anti-terrorist branch, Mr Blair was also on notice that serious questions remain to be answered following a review of all the developments and processes leading up to yesterday's no-warning attack.
Conservative leadership contender and shadow home secretary David Davis urged Mr Blair, or Home Secretary Charles Clarke, to report again to MPs on Monday. At the same time he renewed his party's call on the government to remove responsibility for counter-terrorism from the office of home secretary and appoint a full-time Minister for Homeland Security.
In an emergency statement in the Commons - while the situation was still developing and the precise number of bombings was unclear - Mr Clarke said it was too soon to say who had been responsible.
Mr Davis agreed last night it was also impossible, pending the security review, to know if the bombings raised questions about resources or the efficiency of Britain's security services. With the security agencies credited with having thwarted a number of previous conspiracies to attack London, Mr Davis also acknowledged: "The simple fact is that you cannot provide one hundred per cent protection for a free society."
As mainland train and bus services started to return to normal business, Mr Davis also dismissed suggestions that bag screening could be introduced at all London Underground stations. However, continuing doubts about the preparedness of the British authorities to handle a large-scale emergency will not necessarily have been eased by Mr Clarke's announcement of additional measures to protect other cities.
And while there clearly was no telephonic "chatter" to alert GCHQ listeners to yesterday's planned attacks, ministers are sure to face further questioning about why the official threat assessment was actually reduced in recent weeks - particularly given the build-up to the G8 summit.
Before flying back to the summit last night, Mr Blair said in a televised statement recorded in Downing Street: "This is a sad day for the British people but we will hold true to the British way of life."
In the House of Commons, however, Respect MP George Galloway broke with the domestic consensus, claiming Londoners had "paid the price" for Mr Blair's decision to go to war in Iraq. While "despicable, yes", Mr Galloway told MPs yesterday's attack was "not unpredictable" and predicted it would not be "the last either".