The man believed to be responsible for the attack in Westminster has been named as Khalid Masood, by the Metropolitan Police.
Masood, who died in the attack, was not the subject of any current police investigations, but he had a range of previous convictions for assaults.
The 52-year-old was born in Kent but was believed to have been living in the West Midlands.
PC Keith Palmer, Aysha Frade and American Kurt Cochran were also killed.
Police said there had been no prior intelligence about Masood’s intention to carry out an attack.
But he was known to the police and his previous convictions included GBH, possession of offensive weapons and public order offences.
His first conviction was in November 1983 for criminal damage and his last conviction was in December 2003 for possession of a knife.
He had not been convicted of any terrorism offences.