Terror on the Thames: Four left dead after London terror attack
Driver ploughs into pedestrians
Attacker is shot dead by police
A knife-wielding man went on a deadly rampage at the heart of Britain's seat of power yesterday, smashing a car into pedestrians on London's Westminster Bridge before stabbing a police officer to death inside the gates of the country's parliament.
Four people were killed, including the assailant, and about 40 others were injured in what UK Prime Minister Theresa May condemned as a "sick and depraved terrorist attack".
This morning, Mark Rowley, the Met's senior anti-terror officer revised the death toll down from five to four - the attacker, Pc Keith Palmer, who he stabbed, and a woman in her mid 40s and a man in his mid 50s, who were mown down as the terrorist sped across Westminster Bridge in his car.
He said 29 people had been treated in hospital with seven people in a critical condition.
Mr Rowley said it was still his belief the attacker worked alone and was inspired by "international terrorism", adding that there was no specific information to suggest any further threat to the public.
Lawmakers, lords, staff and visitors were locked down after the man was shot by police within the perimeter of Parliament, just yards from entrances to the building itself and in the shadow of the iconic Big Ben clock tower. He died, as did two pedestrians on the bridge, and the police officer. The fatally wounded policeman, who was unarmed, was named by Scotland Yard as 48-year-old husband and father Keith Palmer.
A doctor who treated the wounded from the bridge said some had "catastrophic" injuries. Three police officers, French teenagers on a school trip and two Romanian tourists were among the casualties.
Police said they were treating the attack as terrorism. There was no immediate claim of responsibility. Britain's top counter-terrorism police officer Mark Rowley said police believed they knew the identity of the attacker but he declined to provide details.
Speaking outside 10 Downing Street, Mrs May said that level would not change. She said attempts to defeat British values of democracy and freedom through terrorism would fail.
"Tomorrow morning, parliament will meet as normal," she said. She said Londoners and visitors "will all move forward together, never giving in to terror and never allowing the voices of hate and evil to drive us apart".
Yesterday was the anniversary of suicide bombings in the Brussels airport and subway that killed 32 people last year, and the latest events echoed recent vehicle attacks in Berlin in Germany and Nice in France.
In the House of Commons, legislators were holding a series of votes on pensions when deputy speaker Lindsay Hoyle announced that the sitting was being suspended and told lawmakers not to leave.
Parliament was locked down for several hours, and adjoining Westminster tube station was shuttered.
The attack began early yesterday afternoon, as a driver in a grey SUV slammed into pedestrians on the bridge.
Former Polish foreign minister Radek Sikorski was in a car crossing the bridge when he heard "something like a car hitting metal sheet" and then saw people lying on the pavement.
"I saw one person who gave no signs of life. One man was bleeding from his head," Mr Sikorski told Poland's TVN24.
Ambulances arrived within minutes to treat people who lay scattered along the length of the bridge, which links parliament to the south bank of the River Thames. One bloodied woman lay surrounded by a scattering of postcards.
Police said one injured woman was pulled from the river.
The car crashed into railings on the north side of the bridge, less than 180 meters from the entrance to parliament.
As people scattered in panic, witnesses saw a man holding a knife run toward the building.
"The whole crowd just surged around the corner by the gates just opposite Big Ben," said witness Rick Longley.
"A guy came past my right shoulder with a big knife and just started plunging it into the policeman. I have never seen anything like that. I just can't believe what I just saw."
The attacker managed to get past a gate into parliament's fenced-in New Palace Yard, a cobbled courtyard in the shadow of the Big Ben clock tower.
'Daily Mail' journalist Quentin Letts said a man in black attacked the police officer before being shot two or three times as he tried to storm into the building.
The attacker fell to the cobbles just yards from the entrance to 1,000-year-old Westminster Hall, the oldest part of the parliamentary complex, busy with visitors and school groups. Beyond that, a corridor leads to the building's central lobby, flanked by House of Commons and House of Lords chambers.
Mrs May was among lawmakers near the Commons at the time of the attack, and was quickly ushered away by security officers and driven back to Downing Street.
As it happened: London reeling as five confirmed dead and 40 injured in attack
To get that far, the attacker would have had to evade the armed officers who patrol the parliament complex in pairs, as well as parliament's own security staff, who don't carry guns.
The attack unfolded near some of the city's most famous tourist sites, including the London Eye, a large Ferris wheel with pods that overlook the capital. It was halted after the attack, stranding visitors in the pods, with an aerial view of the attack scene.
London Ambulance Service said medics treated 12 people for serious injuries and eight who were less seriously hurt.
Dr Colleen Anderson of St Thomas' Hospital said some of the wounded had "catastrophic" injuries. "Some had injuries they could walk away from or who have life-changing injuries," she said.
Three French students on a school trip from Saint-Joseph in the Brittany town of Concarneau, two Romanians and five South Koreans were among the injured.