Scotland Yard's Anti-Terrorist Squad is still seeking the killers of the exiled Bulgarian broadcaster, Georgi Markov. Panorama's major investigation into the 'poisoned umbrella murder' has uncovered startling new evidence.
Michael Cockerell reports on the murky world of intelligence agencies, secret policemen and assassination squads. The film reveals Georgi Markov's political background, his work for the controversial radio station 'Free Europe', and tells how a battle of words with the Communists turned into something much more sinister.