The Westminster attacker was a British citizen who was known to the police and security services and had been investigated some years ago over violent extremism, the Prime Minister has revealed.

Theresa May told MPs he was a “peripheral” figure, adding: “He was not part of the current intelligence picture.”

Delivering a defiant message to a packed House of Commons, Mrs May said: “We will never waver in the face of terrorism.”

The Prime Minister addressed MPs as they gathered at the usual time inside the Palace of Westminster, which a day before had come under attack from the knife-wielding terrorist.

An hour after MPs had stood for a minute’s silence in honour of the innocent people killed in the attack, Mrs May delivered a statement with details of the atrocity.

Paying tribute to Pc Keith Palmer, who died after being stabbed, she said: “He was every inch a hero and his actions will never be forgotten.”

Mrs May concluded her statement by saying: “Our values will prevail.”