Two Sudanese men who had been clinging to the undercarriage of a heavy goods vehicle since it left Calais eight hours earlier started clambering off as it stopped in traffic on the M25 motorway at about 7pm on Friday.

One escaped to a grass verge, but his compatriot fell under the back wheels as the vehicle re-started.

Two  motorists stopped to help the injured man and call for help, but by the time an air ambulance arrived at the spot, between junctions 24 (Potters Bar) and 25(Enfield), he was dead.

The lorry driver drove off without realising what had happened, but police have now traced him.

The unhurt migrant was arrested and was put in custody by immigration officials.

Officers are appealing for witnesses or anyone with information to call the Metropolitan Police

on 0208 9919555 or dial 101 and ask for Alperton Traffic Garage.