London attack: UK's most senior police officer confirms he witnessed the fatal stabbing

Britain's most senior police officer witnessed the terror attack at Westminster, he has confirmed.

Acting commissioner of the Met Police Craig Mackey is being treated as a significant witness as he was on the scene.

He was not one of those injured.

Speaking outside Scotland Yard just yards from the scene of the attack, Mr Mackey said: "I personally was a witness to part of yesterday's events, including part of the tragic attack on PC [Keith] Palmer.

"As with all police officers, I therefore had a duty to secure my evidence and produce statements yesterday evening, which I did before resuming my role leading our response to this incident."

Mr Mackey, who is temporarily in charge of the Met after the retirement of Sir Bernard Hogan-Howe, was Chief Constable of Cumbria Police in 2010 when gunman Derrick Bird shot and killed 12 people.