A man thought to have travelled to Britain clinging to the bottom of a lorry has died after falling beneath the vehicle's wheels on the M25 motorway.

The man, from Sudan, is believed to have climbed underneath the lorry in the French port of Calais.

Police are seeking witnesses to the incident, described as a 'fatal fail-to-stop traffic collision', that took place at 7pm on Friday between junctions 24 and 25 of the M25 in Hertfordshire.

Scotland Yard said two men from Sudan are believed to have got underneath a foreign HGV in Calais at around 11am and wedged themselves into place.

The vehicle they were concealed beneath entered the Eurotunnel and arrived in England about 40 minutes later and began travelling towards London.

At approximately 7pm, police said, the two men, still clinging to the underside of the HGV, decided to leave the lorry after becoming extremely cold.

While the HGV was stationary in lane one of the motorway, one of the men worked himself free and clambered down the nearby grass verge.

Police said the second man attempted to do the same, but the lorry began to move off and he is believed to have fallen beneath its rear wheels suffering fatal injuries.

Another driver stopped his vehicle and pulled the injured man to the edge of the carriageway. He then drove off. A second member of the public stopped his vehicle and offered assistance.

London's Air Ambulance attended and the man was pronounced dead at the scene. Officers are appealing to anyone who saw what happened to come forward.