Bystanders have told of their horror after a police van collided with a pedestrian in Isleworth , leaving him fighting for his life.

Two shopkeepers, who asked not to be named, reported hearing a loud bang, and one told how he saw the man lying in the road, surrounded by a pool of blood.

Police said the van had been responding to an emergency call at the time of the collision in London Road, Isleworth , near the junction with Thornbury Road, at about 10.55pm on Tuesday night (December 8).

They said a 35-year-old pedestrian had been taken to hospital, where he remained this morning in a critical condition.

One shopkeeper told how he understood the man had been crossing the road by a bus stop on the small shopping parade when the crash happened.

There was still a small trickle of what appeared to be blood on the road by the bus stop on Wednesday afternoon.

'There must have been about 19 police cars and vans'

"There was a massive noise and people were saying the man had been crossing the road by the bus stop when he was hit," said one shopkeeper.

Another added: "The guy was lying on the road bleeding heavily from his arm. There was a big pool of blood. Everyone was in shock and people were shouting 'the police van crashed into that guy'.

"There must have been about 19 police cars and vans, and at least 35 or 40 officers there.

"They were operating on the guy for at least 18-20 minutes before he was taken away by ambulance."

Another shopkeeper said he was upstairs when he heard a loud bang, which sounded like two cars crashing into one another.

He said he could not recall hearing sirens beforehand but it is a busy road so he would not have remembered if the police sirens had been operating.

Police have said the van was responding to a 999 call in Brentford and travelling with blue lights on but no sirens.

They said the two officers inside the van, the driver and operator, were not injured.

Anyone who saw the incident is asked to call the witness line at the Serious Collision Investigation Unit at Merton on 020 8543 5157.