The arrest came after extra detectives were drafted in toexamine hundreds of calls from the public following an appeal for information from the dead man's 17-year-old fiancee, Danielle Cable, on television.
Mr Cameron, 21, an electrician from Swanley, Kent, was knifed to death after their Bedford Rascal van, driven by Ms Cable, was "cut up" by a Discovery. The driver stopped at traffic lights at junction three of the M25 at Swanley, punched Mr Cameron as he got out of the van, then stabbed him twice.
The killer drove off towards the Dartford Tunnel, leaving Mr Cameron dying in his fiancee's arms.
The arrested man was taken into custody at Worthing police station, West Sussex, late on Friday night, and a team of four detectives from the murder incident room in Dartford, Kent, travelled to Worthing to interview him.
The Discovery, which was examined by the Kent detectives, was believed to match the type and age of the one driven by Mr Cameron's murderer, but it was not the same colour.
A Sussex police spokesman said the arrested man, who comes from Worthing, was questioned as just one of many possible lines of inquiry. The spokesman had earlier said: "A man is in custody in connection with the theft of a Land Rover Discovery that was stolen from London during the relevant timescale of last week's incident.
"He will be questioned by Kent police specifically in connection with the incident on the M25 motorway, but certainly at this stage there is no evidence linking him to it." A Kent spokesman had said: "We will be interviewing him to establish his involvement in the incident or to eliminate him from the inquiry."