Police are continuing to question a man on suspicion of criminal damage and dangerous driving after a vehicle drove into the gates of Downing Street on Thursday afternoon.
Whitehall was plunged into lockdown and the incident caused panic among tourists and children who fled in terror around 4.20pm.
Prime Minister Rishi Sunak was working at No10 when a male driver slowly veered off the road and hit the gates.
Images on social media showed the Kia car surrounded by emergency vehicles.
The suspect, a white, middle-aged man, was arrested at the scene. The Metropolitan Police said no-one had been hurt.
It is understood counter-terrorism detectives are not involved at this stage.
The PM, who had been due to leave anyway, departed 40 minutes after the crash.
Witness Simon Parry, 44, said he heard a “bang” and saw police pointing Taser guns at a suspect who was wrestled to the ground by firearms officers.
“I heard a bang and looked up and saw loads of police with Taser guns shouting at the man,” he said.
“A lot of police vehicles came very quickly and were very quick to evacuate the area.”
Mr Parry said the driver had his “face to the floor” as he was being arrested.
Asked to describe the mood in the immediate aftermath, Mr Parry said: “We saw people that were in a panic running away and we saw people who were excited.”
Footage of the incident broadcast by the BBC appears to show the car slowing down before it hits the gate.
The incident came as many civil servants were leaving work.
A police cordon was initially put in place in the Whitehall area outside Downing Street, but was later removed. A tow truck then removed the vehicle from the area.