A man arrested after a car crashed outside the Houses of Parliament in a suspected terror attack is a British citizen of Sudanese origin called Salih Khater, the Press Association understands.
It is believed the 29-year-old remains in police custody after his arrest on suspicion of preparing an act of terror.
He reportedly lives in Birmingham, works as a shop manager, and has studied at Sudan University of Science and Technology.
The silver Ford Fiesta used in the attack was driven from Birmingham to London late on Monday and spent almost five hours in the Tottenham Court Road area.
It was then driven around the Westminster area for more than 90 minutes before it crashed into a security barrier just before 7.40am on Tuesday.
Counter-terrorism officers have since conducted searches at two addresses in Birmingham and a residential property in Nottingham as part of the probe.
Plainclothed police officers could be seen outside an address in Peveril Street, Nottingham, on Tuesday evening, said by neighbours to be home to six Sudanese people.
There was also a police presence near the Bunna Internet Cafe on Stratford Road in Sparkbrook, Birmingham, but it was not confirmed whether that was in relation to the Westminster probe.
The suspect, who was said to not be co-operating with officers, was not known to security services, Metropolitan Police counter-terrorism head Neil Basu said.
He said the apparent deliberate nature of the act, the method used and the "iconic" location of Parliament led the force to treat it as a terrorist incident.
Footage aired on BBC News showed the car's approach towards Parliament, where it crossed into oncoming traffic and collided with cyclists before entering a small road and crashing into a security barrier.
Three people sustained non-life-threatening injuries. One man was treated at the scene while another man and a woman were taken to hospital but were discharged by Tuesday evening.
Images posted online showed a man wearing a black puffer jacket being led away in handcuffs from the car as armed police swarmed the scene.
There was nobody else in the vehicle and no weapons were found, police said.
Mr Basu added no other suspects have been identified and there is "no intelligence at this time of further danger" to Londoners.
The car was removed from the scene late on Tuesday night.
After a meeting of the Government's emergency Cobra committee, Theresa May urged the country to come together and carry on as normal.
In a statement the Prime Minister, who is on holiday, praised the "formidable courage" and professionalism of the emergency services who "ran towards" danger.
Home Secretary Sajid Javid, who also thanked the emergency services, urged people to "keep an open mind" about the incident.
US President Donald Trump said on Twitter: "These animals are crazy and must be dealt with through toughness and strength!"
All the details as they happened on the day of the Westminster crash
Witnesses described an emotionless driver ploughing through cyclists in what appeared to be a deliberate act.
Kirsty Moseley, of Brixton, was a passenger in the first car behind the cyclists, who "were thrown everywhere" after being struck at what she estimated was 25mph.
Ms Moseley, 31, added: "He (the driver) wasn't shouting anything, he wasn't screaming, he didn't look crazed or out of control - he was just deadpan."
Jason Williams, from Kennington, was walking to work when he saw the "deliberate" crash.
"It didn't look like an accident. How do you do that by accident? It was a loud bang," the 45-year-old told PA.
The Houses of Parliament are surrounded with security barriers of steel and concrete.
The measures were extended after the Westminster Bridge attack in March 2017 when Khalid Masood ploughed a car into crowds on Westminster Bridge, killing four people.
Masood abandoned his car then fatally stabbed unarmed Pc Keith Palmer before he was shot by armed police in a courtyard outside Parliament.
The terrorist threat against the UK is seen as unprecedented.
The Prime Minister's official spokesman said there were 676 live investigations being carried out by the security services and counter-terror police at the end of June, up from more than 500 in March.
Some 13 Islamist plots and four by far-right extremists have been foiled in the past 18 months, he added.
There are roughly 3,000 active "subjects of interest" at any one time - while there is also a wider pool of more than 20,000 individuals who have featured in probes whose threat must be kept under review.