Trivia: This is the only episode in which we see John Tracy taking part in a rescue.
Trivia: The Manor to Penelope's right at the Clydeside launching of "Ocean Pioneer II" is Professor Holden from "The Mighty Atom". Tony Williams (from "Cry Wolf"), MI5 agent Tidman (from "The Man from MI5") and Lovegrove (from "The Vault of Death") are also visible in the crowd, as well as the Commander of "Ocean Pioneer I".
Trivia: Lord Worden was originally seen as Sir Jeremy Hodge in the episode "The Perils of Penelope".
