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Labour MP Mary Creagh arrived at the scene shortly after the incident.

She told the BBC: "When we were on our way to vote there were armed police officers standing at the escalator.

"As I got off the escalator I saw people running towards me. Penny Mordaunt [another MP] ran up and said 'shots have been fired, we need to get out now'.

"We had no choice but to go out of the revolving doors one at a time - I shouted to the security guard 'you've got to open the doors' and he then opened them.

"I found myself in Westminster Tube station, I thought the one thing we don't want is tourists wandering in with their children into this situation.

"I went into the control room and told the controller 'there's been what we think is a terror attack on the Palace of Westminster and I said 'you need to shut the station now'."