Metropolitan Police Commissioner Sir Mark Rowley has described the prosecution of an officer who crashed while driving to the scene of a terror attack as “appalling”.

Pc Paul Fisher, 46, made a “split-second error” when he lost control of his unmarked BMW X5 and ran into the back of a taxi driver’s Toyota, before hitting a Ford Fiesta and a wall, en route to the scene of the stabbing spree carried out by terrorist Sudesh Amman in Streatham, south London, in February 2020.

The officer described the moment he found out the terrorist had begun stabbing people as “pandemonium”, and went to the scene at more than 80mph because he believed Amman “might be wearing a suicide vest”.

Prosecutors said Fisher’s “extreme speed” and risky manoeuvres amounted to dangerous driving, but he was cleared on Friday after five hours of jury deliberation at Southwark Crown Court, almost four years after being charged.

Speaking outside court after the verdict, Sir Mark said the case “undermines the confidence of all officers using their powers to keep the public safe”.

He added: “Thank god for the common sense of British juries.

“Paul Fisher is a firearms officer who was under the most unimaginable pressure.

“He clearly made some mistakes on that drive, the right answer would have been some warnings within the organisation, some re-training, some re-testing to getting back to protecting the public.”

The Independent Office for Police Conduct (IOPC) said “rigorous independent scrutiny is not a threat to policing”.

Pc Fisher, a former Royal Marine, said he “let people down” but denied dangerous driving.

Giving evidence, he said: “At no point did my colleagues turn around and say ‘Paul you’re driving too fast’. I would have stopped.”

He was responding, with two other armed officers in his vehicle, to the stabbing carried out by Amman in February 2020.

Aman, 20, grabbed a large kitchen knife from a hardware store on Streatham High Road in south London and stabbed two people at random.

The officer was on a surveillance operation at the time of the crash, monitoring Amman after his release from jail 10 days earlier.

Fisher was waiting with other armed officers at a local police station while undercover units followed more closely.

Having been told over the radio that Amman had begun stabbing people, Pc Fisher began his journey from Gypsy Hill police station in Crystal Palace to Streatham High Road, about three miles away.

On-board camera footage showed Fisher driving at high speed as he overtook people and squeezed the BMW SUV through narrow gaps in the traffic.

The police car did not have its blue lights on at the time because they had accidentally been switched off by his passenger.

The vehicle, which did have its siren on, had been switched to “arrival mode” and only had flashing rear red lights displayed.

As Fisher went for another overtake at Streatham Common, his vehicle lost grip on a turn and he hit a taxi driver’s Toyota.

He said: “I remember braking for the bend but the vehicle seemed to drift.

“I started emergency braking and steering to the right in an attempt to avoid the vehicle.”

Defending Fisher, Kevin Baumber said: “The last thing (he) intended was any kind of harm at all.

“Not all collisions are crimes.”

Police officers going to the scene of an emergency are exempt from certain driving laws, including following the speed limit, obeying traffic lights and keep left signs.

But prosecutor Ben Lloyd said that getting to the scene of the incident provided Fisher with “no defence for dangerous driving”.

The drivers of the two vehicles which Fisher’s car collided with, a man and a woman, were left with minor injuries.

The female officer in the back of the police car suffered a cut head and Fisher was bleeding from the ear after the crash.

Tom Whiting, IOPC acting director general said: “The fundamental principle of policing by consent is a precious part of British society which we should celebrate.

“Rigorous independent scrutiny is not a threat to policing, it is a protection and helps the police do their job by making sure they are getting things right and supporting them to fix it when things go wrong.

“We know that accountability and scrutiny can feel deeply uncomfortable for the individuals and organisations involved, but if they are weakened, there is a real risk to public trust.

“We welcome the Home Office review as it is an opportunity to make improvements to the system.”

IOPC regional director Mel Palmer said: “There is no doubt that Pc Fisher was responding to a life-threatening incident in February 2020.

“Prior to the crash, Pc Fisher was found to be driving at more than four times the speed limit.

“This, along with other evidence, led us to passing a file to the CPS (Crown Prosecution Service).”

A CPS spokesman said: “The CPS does not decide whether a person is guilty of a criminal offence, we make fair, independent and objective assessments about whether it is appropriate to present charges for the court to consider.

“In this case, we decided it was appropriate for a court to consider one charge of dangerous driving. The jury found the defendant not guilty and we respect its verdict.”