The man believed to have carried out the attack in Westminster has been named by police as Khalid Masood.
Kent-born Masood, who died in the attack, was not the subject of any current police investigations, but had a range of previous convictions.
The 52-year-old was believed to have been living in the West Midlands.
The so-called Islamic State group has said it was behind the attack, in which PC Keith Palmer, Aysha Frade and US tourist Kurt Cochran were killed.
Eight arrests were made in London and Birmingham following Wednesday's attack.