The Prime Minister, Theresa May, has said that 'our values will prevail' as she revealed that the man who carried out the attack on Westminster yesterday was British-born and had been investigated 'some years ago' by MI5.

Addressing a packed House of Commons chamber today, May said that the attacker was 'once investigated by MI5 in relations to concerns about violent extremism'. She added that he was a 'peripheral figure' and that 'intensive investigations continue'.

The Prime Minister said that it appears that the attacker was 'inspired by Islamist ideology'. She added: 'We know the threat from Islamist terrorism is very real.'

May said that millions of ordinary Londoners were showing that terrorism can be defeated by carrying on with their lives as normal. 'The greatest response lies not in the words of politicians, but in the everyday actions of ordinary citizens,' she said.

'Yesterday we saw the worst of humanity, but we will remember the best...Let this be the message from this House and this nation today: our values will prevail.'

May praised the police, who 'heroically did their job' and paid tribute to efforts to save the life of PC Keith Palmer, who died in the incident, including help given by the Conservative MP, Tobias Ellwood.

The PM said of PC Palmer: 'He was every inch a hero and his actions will never be forgotten.'

After May had finished speaking, the Commons Speaker, John Bercow, pointed out that MPs had been joined in the gallery by the French foreign minister, Jean-Marc Ayrault.