Notable as the first live-action Gerry Anderson production and the only one to date without some form of fantasy element in it.
The pinball machine that Paddy plays in the cafe is an "Ace High" made by D. Gottlieb & Co. from 1957.
The opening title music was a flute and orchestral arrangements of The Shadows' "Man of Mystery".
Not originally part of the Edgar Wallace Mysteries but subsequently incorporated into the series also distributed by Anglo-Amalgamated and re-edited with new opening titles.