British police named the man who killed three people near the UK parliament before being shot dead as Khalid Masood, saying he had a string of criminal convictions but none for terrorism-related offences.
Masood, 52, was born in Kent to the southeast of London and had been most recently living in central England, London police said. Known by a number of other aliases, he had not been convicted previously for any terrorism offences, they added.
"Masood was not the subject of any current investigations and there was no prior intelligence about his intent to mount a terrorist attack," they said in a statement.
"However, he was known to police and has a range of previous convictions for assaults, including GBH (grievous bodily harm), possession of offensive weapons and public order offences."
Police said his first conviction was in November 1983 for criminal damage and his last was in December 2003 for possession of a knife.
The English teacher and bodybuilding fan had previously been on intelligence service MI5's radar.
"The man was British-born and that - some years ago - he was once investigated in relation to concerns about violent extremism. He was a peripheral figure," said Prime Minister Theresa May.
"The case is historic - he was not part of the current intelligence picture. There was no prior intelligence of his intent - or of the plot. Intensive investigations continue."
Islamic State has claimed responsibility for the attack.
Meanwhile, all eight people arrested in a series of raids overnight are suspected of preparing terrorist acts, London police said on Friday.
Detectives were still searching properties in Wales, the central city of Birmingham and east London.
Hundreds of detectives are involved in the investigation.
The link to central England tied in with the news that the car used in the attack had been hired from rental company Enterprise's Spring Hill branch in Birmingham.
Seven people were arrested in a raid on a Birmingham flat following the attack. One of those killed was Masood, who was shot dead at the scene.
Streets around Trafalgar Square will be closed for a candlelit vigil from 7am (NZ time).
The victims have been named as:
- Keith Palmer, 48, a police officer killed trying to subdue the attacker
- Aysha Frade, 43, who worked at DLD College London, not far from the site of the attack
- Kurt Cochran, 54, a US citizen in London to celebrate his 25th wedding anniversary.
Reuters / Newshub.