A police officer critically injured in a hit and run in Sutton has died.

PC Andrew Duncan,a Merton traffic officer, was rushed to hospital on Friday morning after he was mowed down by a car travelling at speed he had signalled to pull over.

The incident happened at about 1am on Reigate Avenue near the Rosehill junction in Sutton.

PC Duncan, known as Andy, died today in hospital from his injuries.

A man arrested on Friday on suspicion of causing serious injury while dangerous driving has now been arrested on suspicion of murder. He remains in police custody. 

Metropolitan Police Commissioner, Sir Bernard Hogan-Howe, said: "I was so sad to hear that PC Andrew Duncan died this morning.

"On behalf of the Metropolitan Police family, I would like to offer my sincere condolences to his wife and children, parents, family and friends.

"Andy was a hard working and courageous policeman. He served the community as both a police officer and as a Scouting volunteer.

"The night he was injured, he was doing a job that he loved and we all had every right to expect he would return safely to his home and family - tragically that was not the case.

"We will continue to professionally and objectively investigate this incident under the oversight of Her Majesty's Coroner.

"I would urge anyone with information to contact us."

PC Duncan was married with two children, a son and a daughter. He was 47 years old.

He joined the Metropolitan Police Service on 19 March 1990 and was originally posted to Battersea.

Six years later he transferred to the South-West Territorial Support Group where he served for almost seven years before moving to Hammersmith and Fulham Borough. He subsequently joined the South-West Traffic Unit on May 17, 2004.

He was working out of its traffic garage in Merton when he was killed.

PC Duncan was critically injured when working on a speed enforcement operation with a colleague, when he noticed a black VW Golf driving at speed along Reigate Avenue toward Rosehill.

PC Duncan attempted to stop the car by signalling for the driver to pull over but the car hit him and drove off towards Rosehill.

The car was found abandoned on Friday morning nearby in Hyde Walk in Morden. It was taken away for forensic examination.

Police officers searched the area around the abandoned car for any clues to aid their investigation.

Officers are continuing to appeal to anyone who was a passenger in the car at the time of the collision to come forward.

Police are also appealing for any witnesses who may have seen the incident to get in touch with the investigation team.

Police said it was possible that people were looking out their windows at the time, or may have been out in the street.

Detectives from the Homicide and Major Crime Command are investigating.Anyone with any information is asked to contact the police incident room on 020 8721 4205.

Did you know PC Andy Duncan? Leave a tribute in the space below, or email mwatts@london.newsquest.co.uk.