Four people have died and 40 people have been injured in a terror attack near the Houses of Parliament. Here is what we know so far.
At 14:40 GMT on Wednesday the man police believe carried out the London attack, Khalid Masood, drove a car that he’d hired from a depot in Birmingham over Westminster Bridge, near the Houses of Parliament.
One witness said he sped up, mounted the pavement, and began hitting pedestrians indiscriminately.
Two people, Aysha Frade and US tourist Kurt Cochran, were killed and dozens more were injured. One woman was seen falling into the River Thames and was subsequently pulled to safety and given urgent medical attention.
Witnesses described seeing figures lying on the pavement. One man said he saw a single trainer on one side of the road, and a body on the other.
The car then crashed into railings outside the Houses of Parliament.
Masood, armed with a knife, left his car and ran towards Parliament, where he was confronted by police.
PC Keith Palmer – who was not armed – was stabbed and killed.
Masood was then shot dead by armed officers.
What was the scene on Westminster Bridge?
Witnesses have described pandemonium and panic.
One, Michael Adamou, 25, was driving the 453 bus when he saw a grey Hyundai heading towards the Houses of Parliament and hitting pedestrians on the bridge.
“Initially I thought he’s lost control of the car, but then I saw quite a few people rushing into Parliament and police trying to stop everyone.
“After a few seconds I just heard gunshots. Everybody on my bus was panicking.”
Another, Richard Tice, said he was coming out of Westminster Tube station at about 14:45 and was ushered by police onto Westminster Bridge.
He saw people lying on the bridge being tended to. He was told that a car had mounted the pavement and driven the whole way, from south to north, across the bridge, knocking people over.
“I counted eight people the length of the bridge, from south to north – at least eight.”
What happened at Parliament?
After crashing into railings outside the Houses of Parliament, Khalid Masood abandoned his car and ran through the cobbled entrance – Carriage Gates.
He attacked PC Keith Palmer with a large knife before being dead by armed police.
Tobias Ellwood, a Conservative foreign office minister and former soldier, attempted to revive PC Palmer before medics arrived.
They struggled for up to half an hour to help the police officer and the attacker, but both men died at the scene.
Parliament was suspended and politicians, journalists and visitors to the buildings were locked inside for about five hours.
Hundreds were also evacuated from Parliament to nearby Westminster Abbey for safety.
Who were the victims?
The police officer who died was PC Keith Palmer, 48, of the Parliamentary and Diplomatic Protection Command. He had 15 years’ service and was a husband and a father.
Paying tribute to PC Palmer in the Commons, Prime Minister Theresa May said he was “every inch a hero and his actions will never be forgotten”.
Aysha Frade, who worked at DLD College London, was killed after being hit by the attacker’s car before it reached Parliament. She was confirmed dead by a doctor at St Thomas’ Hospital.
It is thought she was 43 and a married mother of two. The college’s principal, Rachel Borland, said Mrs Frade “was highly regarded and loved by our students and by her colleagues”.
“She will be deeply missed by all of us,” she added.
A third victim has been named as Kurt Cochran – a US tourist who was in London to celebrate his 25th wedding anniversary. His wife Melissa has been seriously injured and is in hospital.
The pair were due to return to the US on Thursday.
In a statement, the couple’s family said: “We express our gratitude to the emergency and medical personnel who have cared for them and ask for your prayers on behalf of Melissa and our family.
“Kurt will be greatly missed.”
Who are the injured?
Seven people are still in a critical condition. A further 29 have been treated in hospital.
The injured included three police officers who were walking across the bridge on their way back from a commendation ceremony. Two are described as being in a serious condition.
Speaking to MPs, Theresa May said those injured in the attack included 12 Britons, three French children, two Romanians, four South Koreans, two Greeks, and one each from Germany, Poland, the Irish Republic, China, Italy and the US.
Four university students from Edge Hill University, in Lancashire, were hurt. Owen Lambert and Travis Frain were struck by the car on Westminster Bridge at the outset of the attack, while two other students needed treatment for lesser injuries.
London Ambulance Service said it had treated 12 people with serious injuries, who were all taken to hospital. They also treated eight people with less serious injuries at the scene.
King’s College Hospital said eight patients were being treated there – six male, and two female. Two were described as critical and two stable
St Thomas’ Hospital said two patients had been admitted – both were stable.
One patient was admitted to the Royal London Hospital, but no details were given.
Who was the attacker?
The attacker has been named as Khalid Masood.
The 52-year-old was born in Kent but is believed to have been living in the West Midlands.
The prime minister told the Commons he had acted alone and there was “no reason to believe” further attacks were planned.
She added that he had come to the attention of the security service, MI5, some years ago over concerns about violent extremism.
Mrs May told MPs: “He was a peripheral figure. 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.”
Acting Deputy Commissioner Mark Rowley, the Met’s top anti-terror officer, said police were focusing on his “motivation, preparation and associates”.
Eight people have been arrested and several addresses raided in London and Birmingham in connection with the attack.
What security has been put in place?
Both the House of Commons and the House of Lords have sat on Thursday at their normal times.
Police said there would be more unarmed and armed police officers on the streets in the coming days, both in London and across the country.
The UK’s threat level has been set at “severe” – meaning an attack is highly likely – for some time and this would not change, the prime minister said.
What about travel in the area?
Westminster Tube station has now reopened and Westminster Bridge is no longer closed to traffic.