This is how events unfolded in the Westminster attack:

2.40pm

Police outside the Palace of Westminster
(Victoria Jones/PA)

Emergency services were called to an incident in the area of Parliament Square.

It emerged that an attacker, armed with two large knives, mowed down pedestrians with his car on Westminster Bridge, including schoolchildren, then rushed at the gates in front of the Houses of Parliament, stabbing a policeman before being shot dead by other officers.

MPs were told the chamber would “remain in lockdown” until further notice and business was suspended.

3.30pm

Police close to the Palace of Westminster
(Victoria Jones/PA)

Scotland Yard said the attack was being treated “as a terrorist incident until we know otherwise”.

4pm

emergency services attend the scene outside the Palace of Westminster
(Stefan Rousseau/PA)

The first death was confirmed when a junior doctor at St Thomas’ Hospital said one woman had died and a number of others were hurt – including some with “catastrophic” injuries.

4.50pm

Commander BJ Harrington of the Metropolitan Police said there were “a number of casualties” in the attack “including police officers”.

5pm

London Ambulance Service said that at least 10 patients were treated on Westminster Bridge and a number of hospitals were on alert.

5.40pm

Emergency services at the scene outside the Palace of Westminster
(Stefan Rousseau/PA)

Sources said a police officer stabbed at the Houses of Parliament had died.

6pm

Mark Rowley, Assistant Commissioner for Specialist Operations in the Metropolitan Police
(Victoria Jones/PA)

Scotland Yard’s top anti-terror officer Mark Rowley confirmed four people were killed, including the police officer who was stabbed and his attacker.

6.45pm

Prime Minister Theresa May makes a statement in Downing Street
(Richard Pohle/The Times/PA)

A spokesman for 10 Downing Street said Prime Minister Theresa May will chair a meeting of the Government’s emergency Cobra committee to discuss the immediate response to the incident in which at least 20 other people were injured. She ordered flags to be lowered to half mast over Downing Street as a mark of respect to the innocent people who lost their lives, and a spokesman said she was being kept updated about the investigation.

9pm

Prime Minister Theresa May described the Westminster attack as “sick and depraved”. Mrs May praised the “exceptional bravery” of police during the attack and said any attempt to defeat the values that Parliament stands for are “doomed to failure”.

10.30pm

The fatally wounded policeman, who was unarmed, was named by Scotland Yard’s top anti-terror officer Mark Rowley as 48-year-old husband and father Keith Palmer.

Mr Rowley told reporters that the death toll had been updated to five – including Mr Palmer, the suspect, and three members of the public.