HOW IT UNFOLDED

WEDNESDAY, MARCH 22

Emergency services are called at 2.40pm to an incident in the area of Parliament Square. An attacker, armed with two large knives, has mowed down pedestrians with his car on Westminster Bridge, then rushed at the gates in front of the Houses of Parliament, stabbing a policeman before being shot dead

About 3.30pm, Scotland Yard says the attack is being treated “as a terrorist incident until we know otherwise”

The first death is confirmed after 4pm, when a doctor at St Thomas’s Hospital says one woman has died and a number of others have been hurt

Before 5.40pm, sources say the police officer who was stabbed has died

About 6pm, Scotland Yard’s top anti-terrorism officer, Mark Rowley, confirms four people were killed, including the policeman and his attacker

After 7pm, Prime Minister Theresa May chairs a meeting of the emergency Cobra committee

THURSDAY, MARCH 23

Before 7.45am, Mr Rowley says six addresses have been raided and seven people arrested across London, Birmingham and elsewhere. He confirms the death toll stands at four and 29 people were treated in hospital

Shortly after 8am, Defence Secretary Michael Fallon says the working assumption is the Westminster attack is linked to Islamic terrorism

Shortly after 10.30am, Ms May tells the Commons the Westminster attacker was a British citizen, who had a criminal past and was known to security services

Less than two hours later, his supposed affiliation is made clear when Islamic State claims he was one of its “soldiers”

At 3.30pm, the attacker is identified as Khalid Masood

By evening, police have arrested eight people in connection with the attack

Mourners gather in Trafalgar Square for a candlelit vigil