Was commonly shown theatrically in the UK as the supporting feature to the original cinema release of Carry on Henry VIII (1971).
Failed TV pilot, The Persuaders got the green light instead. Later released theatrically as a support picture to the main..
Writer Philip Levene originated the idea in his BBC Light Programme radio series "Destination - Fire!" which ran for 33 episodes across 1962-66. In this run Quentin Barnaby was played by Robert Beatty and Valerie Chrane by Gudrun Ure.
Most of the crew had previously been working on 'The Avengers'.