Footage of the moment a motorcyclist smashed into a pedestrian and rode off after shouting at the unconscious man has been released in an attempt to hunt down the "heartless" biker.

The CCTV video shows the moment the man, understood to be Dr Tim Wilks, a programme director for Epsom & St Hospitals, is knocked out by the collision.

As Your Local Guardian reported on Saturday the hit and run happened at about 12.30am on February 28 as he was crossing Malden Road at the junction with London Road in Cheam.

The footage begins with the pedestrian crossing the road just before traffic begins to move off. As he is about to reach the traffic island the motorbike comes into view and he is sent careering down the road and knocked out.

Dr Wilks, a 53-year-old father of three, was taken to St George's Hospital for treatment. He has since been discharged and remains off work due to his injuries.

The rider, who was also knocked off his bike during the collision, is then seen to get up and "angrily berate the stricken pedestrian before getting back on his motorcycle and driving off down Cheam Common Road", the Metropolitan Police said.

As the biker rides off, a car which was waiting at traffic lights at Malden Road follows the motorcycle down Cheam Common Road.

Detective Sergeant Dave Jarvis of Sutton police said: "It would have been obvious to the rider of the motorcycle that the pedestrian he had collided with was seriously injured.

"To act in the way he did, shouting at the unconscious man and driving off from the scene without attempting to seek medical help, was a truly heartless act."

Officers are appealing to anyone who witnessed the crash or has any information about the identity of the motorcycle rider.

They would also like to speak with the occupants of the white car as they believe they may be able to assist the investigation.

To help call Sutton police on 101 or Crimestoppers, anonymously, on 0800 555 111.

No arrests have been made and enquiries continue.