The Government's emergency response committee, Cobra, reconvened last night to discuss security measures following the first terrorist murder on the British mainland since the 7/7 suicide bombings of 2005.
Security has been increased at army barracks across London after two men - believed to be British citizens of Nigerian background - attempted to behead a soldier in front of dozens of witnesses.
Both were shot and wounded by the police who took 20 minutes to arrive. They are under armed guard in hospital. They are not thought to have links to militant groups based in Nigeria such as Boko Haram.
After the killing, one of the men, named by the Sun last night as Michael Adebolajo, spoke calmly into a witness's video phone. Speaking with a London accent, holding a knife and a meat cleaver and with his hands dripping with blood, he said: "We swear by almighty Allah we will never stop fighting you until you leave us alone. Your people will never be safe. The only reason we have done this is because Muslims are dying by British soldiers every day.
"We must fight them as they fight us. An eye for an eye and a tooth for a tooth. I apologise that women had to witness this today but in our lands our women have to see the same. You people will never be safe. Remove your government, they don't care about you."
Mayor of London Boris Johnson, leaving the Cobra meeting, appeared to indicate that the attack was being seen as a one-off incident.
"Everything I am hearing leads me to think that Londoners can go about their business in the normal way and we are going to bring the killers to justice". Earlier he said: "The people of London should take their cue, from the behaviour of the people of Woolwich, who showed such astonishing natural courage." Johnson said the blame for the event lay not with Islam or British foreign policy but "wholly and exclusively in the warped and deluded mindset of the people who did it".
The far-right and the English Defence League are using social media to exploit the attack. Riot police contained an EDL demonstration in Woolwich. Elsewhere, two men were arrested following attacks on mosques.
Witnesses said that the assailants used a car to run over the soldier just metres from the Royal Artillery Barracks in Woolwich, southeast London, before attacking him with knives and a meat cleaver.
The victim, who was wearing a Help for Heroes military charity T-shirt, was aged around 20, and had reportedly been on duty at an Army recruitment office in central London and was heading back to the barracks.
'It is you versus many, you are going to lose'
A mother-of-two told how she put her life on the line by trying to persuade the extremists to hand over their weapons.
Ingrid Loyau-Kennett, a Cub Scout leader, talked to the killers and kept her nerve as one of them told her: "We want to start a war in London tonight."
Loyau-Kennett, 48, from Cornwall, was one of the first people on the scene.
She was on a bus which was travelling past and jumped off to check the soldier's pulse. "I have my first aid ... I thought it was an accident. Then I saw the guy was dead ... And then when I went up there was this black guy with a revolver and a kitchen knife.
"He had what looked like butcher's tools and he had a little axe, to cut the bones, and two large knives and he said: 'Move off the body.' ... He was covered with blood. I thought I had better start talking to him before he starts attacking somebody else ...
"I asked him if he did it and he said yes and I said why? And he said because he has killed Muslim people in Muslim countries.
"He said [the victim] was a soldier ... 'I killed him because he killed Muslims and I am fed up with people killing Muslims in Afghanistan.'
"He was not high ... he was not ... drunk. He was just distressed, upset. He was in full control of his decisions ... I said: 'Right, now it is only you versus many people, you are going to lose, what would you like to do?' He said: 'I would like to stay and fight'."
Loyau-Kennett then talked to the man in the light coat. "I said: 'Would you like to give me what you have in your hands?' I did not want to say weapons but I thought it was better having them aimed on one person like me rather than everybody there."
Other people shielded the soldier's body as the killers stood over them. Joe Tallant, 20, said a friend and her mother went over to help the soldier.
"Her mother was so brave, she didn't care what happened to her. She knelt by his side and comforted him. She held his hand and put her other hand on his chest. I think she might have been praying."