Police have identified Khalid Masood as the man who carried out the Westminster attack, as the death toll rose to five.
Masood, 52, was born as Adrian Elms in Kent and was shot dead by police. He had not been the subject of any current police investigations.
PC Keith Palmer, 48, Aysha Frade and US tourist Kurt Cochran, 54, were killed on Wednesday, while a 75-year-old man died on Thursday evening.
The so-called Islamic State group has said it was behind the attack.Three women and five men were arrested in London and Birmingham on suspicion of preparation of terrorist acts following Wednesday's attack.
A woman aged 39 was arrested in east London
A 21-year-old woman and a 23-year-old man were arrested in Birmingham
A 26-year-old woman and three men aged 28, 27 and 26 were arrested at another address
A man aged 58 was arrested at an address in Birmingham
The Met Police says detectives are continuing to search a number of addresses, including one in Carmarthenshire, three in Birmingham and one in east London. Addresses in Brighton and south-east London have also been searched.Home Secretary Amber Rudd told those gathered for a candlelit vigil in London's Trafalgar Square on Thursday evening that terrorists "will not win".
"We are all connected and today we showed that by coming together, by going to work, by getting about our normal business, because the terrorists will not defeat us. We will defeat them," she said.
Masood drove into pedestrians on Westminster Bridge before crashing his car into railings and then running into the grounds of Parliament, armed with a knife.
He stabbed PC Palmer before being shot dead.
The Metropolitan 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 causing grievous bodily harm, possession of offensive weapons and public order offences. He was believed to have been living in the West Midlands.
Masood is believed to have lived at various times in Crawley, West Sussex, and Rye and Eastbourne, both in East Sussex.
He also appears to have been convicted of a knife crime in 2003 in Eastbourne.
His first conviction was in November 1983 for criminal damage and his last in December 2003 for possession of a knife.
He had not been convicted of any terrorism offences.
Car hire company Enterprise said the vehicle used in the attack had been rented from its Spring Hill depot in Birmingham.
The BBC understands Masood hired the Hyundai SUV in person, giving his profession as a teacher.
The Department for Education said it had no record of him having worked as a qualified teacher in English state schools.