Episodes 21-24 (the majority of "The Day of the Clone") were made in black & white due to union action over a technicians' pay dispute at ITV (which effectively prevented any sales to US stations). However, although all of the episodes exist as monochrome 16mm film prints, only the sixth episode of "The Time of the Ice-Box" is known to still survive as an original colour videotape copy.
The 26 episodes consist of four self-contained stories: - "The Wrong End of Time" (6 episodes) - "The Time of The Ice Box" (6 episodes) - "The Year of The Burn Up" (8 episodes) - "The Day of The Clone" (6 episodes).
Both _"Ripping Yarns: Tomkinson's Schooldays (#1.1)" (1976)_ and Telly Savalas Looks at Portsmouth (1981) feature blasts of "Timeslip"'s theme-tune. This is because the piece is stock music (and thus available to any production company) by Edouard Michaël, 'Rite de la Terre' from 'Quatre Rituels Pour Orchestre', from the DeWolfe library.
Peter Fairley, science correspondent for UK TV news company ITN, introduced the first two stories on-screen.
As specified in "The Year of The Burn Up", Simon Randall is aged 16; Liz Skinner is 15. Originally Liz was only to be 13, but the production team decided that Cheryl Burfield was too physically mature for this to remain viable.
The Naval Station location of the time barrier is sited at the Ministry field of St. Oswald's.
The Antarctic Ice Box, based at the South Pole, is the International Institute for Biological Research, run by the International Commission.
Commander Charles Traynor founded the Ministry of Forward Development in December 1970. When the series originally aired, this date was contemporaneous with "The Year of the Burn Up", in which it first features.
The series was originally planned as a six-part one. This was then expanded to thirteen, and ultimately 26 editions.
Script editor Ruth Boswell and her husband James came up with the central concept of the series, and appointed producer John Cooper brought New Zealand writer Bruce Stewart (II) in to pen and flesh out the stories. Another engagement in his scripting diary meant that Victor Pemberton handled the final seven episodes.
SPOILER: The visceral sequence of Dr Joynton aging to death in "The Time of the Ice Box" was edited down by ITV when the series was repeated in 1973/4, following viewer complaints on the original transmission.
Science-fiction author Geoffrey Hoyle acted as scientific advisor on the show.
The first two stories were adapted by an uncredited James Boswell (II) into a novelisation for Pan Books, reprinted the following year by Piccolo Books. The book reveals that St. Oswald's is located in Rutland.
The regular cast were very close: Spencer Banks and Cheryl Burfield are still friends (her husband was best man at his wedding), and godparents to each other's children.
"Look-in" magazine ran a comic-strip based on the show in 1971.
This is the only known episode of the series to have survived on its original colour videotape, rather than just as a monochrome film recording.