The Met Police’s acting commissioner witnessed the murder of PC Keith Palmer during the Westminster attack from inside his car, an inquest has heard.

Sir Craig Mackey said it was his instinct to get out of the car when he saw Khalid Masood attack, but he stayed because he had no protective equipment.

The attack happened as he was being driven out of the Palace of Westminster after a meeting on 22 March last year.

Masood also drove into and killed four people on Westminster bridge.

The 52-year-old was shot dead by armed police during the attack and his inquest is taking place at the Old Bailey in central London. The inquest into the deaths of PC Palmer, 48, Kurt Cochran, 54, Leslie Rhodes, 75, Aysha Frade, 44, and Andreea Cristea, 31, finished last week – the coroner ruled all five been unlawfully killed.

Sir Craig, now deputy commissioner of Scotland Yard, had been at the House of Commons meeting then-police minister Brandon Lewis.

As he was driven out of the Palace of Westminster with colleagues, he heard a “very, very loud bang” from the direction of Westminster tube station.

He said they then locked the car’s doors as they saw Masood with a large knife at the gates. “There was quite a lot of confusion about what was going on,” Sir Craig told the Old Bailey. “Clearly the way that the male came in and the purposeful way he came, he was clearly a threat.”

Sir Craig, who retires in December, said he saw PC Palmer suffer “two determined stab wounds”. He said: “I could see PC Palmer moving backwards and him going down… “The thing that still shakes me about the attack is that it was 80-plus seconds in total. It didn’t feel like that, it felt an awfully long time.”

Masood was then shot by a close protection officer.

When asked what his reaction was following the gunshots, Sir Craig said: “First and foremost I was a police officer so I went to open the door to get out. “One of the PCs, quite rightfully, said: ‘Get out, make safe, go, shut the door,’ which he did, and it was the right thing to do. “That’s when I thought: ‘I have got to start putting everything we need in place. We have got no protective equipment, no radio, I have got two colleagues with me who are quite distressed,’ so we moved out.”

He added: “If anyone had got out, the way this Masood was looking, anyone who got in his way would have been a target.”

The inquest has adjourned until Wednesday, when two close protection officers will give evidence.