It was about the M25 and was entitled "The Magic Roundabout" It dealt with some of the incidents the Police had to deal with and specifically, one, a fatal accident involving a lorry driver whose body was found, inexplicably, some distance from his lorry. It also used Thomas Tallis' "Spem in Alium" as the title music.
It was one of a series of regular documentaries along the lines of Horizon, Equinox, World in action etc. etc.
Does anybody have any more detail about it please or possibly even a source where I can get a copy?
I can't be sure but I think it was produced in the Eighties or Nineties.