When the attack happened in Westminster people thought a bomb had gone off and "all hell was breaking lose," says a journalist who witnessed the chaos.
A car has mown down several pedestrians on Westminster Bridge while an attacker wielding a knife attacked a policeman before being gunned down. One woman has died on Westminster Bridge.
The Sun's Tom Newton Dunn was at a nearby restaurant near Parliament. Just before the attack some MPs had left it to go to a vote, but he was still inside.
He said: "All hell was breaking lose on the main street outside Parliament, the PM’s Jaguar came at some considerable speed out of the [House of Lords] entrance.
"It sped right by the river here and sped past me at incredible speed with protection officers in the land rover behind her."
Dunn added that at first “the feeling was a bomb had gone off, there were people sprinting from the direction of Westminster" and those nearby had no clue what had happened.
“I had MPs and even one minister ringing me from inside the building saying 'what’s going on?'
The editor believes: “For something like this to happen, it’s really an attack on the country itself, on democracy."
Listen to the full interview above