As far as the BBC Archives are concerned only 16 of the 52 editions are currently held by them: 11 on the BBC's original colour masters as transmitted, and the final five episodes as monochrome film prints returned from New Zealand. BetaFilm and/or ZDF in Germany do hold 35mm colour telerecordings of all 39 episodes from the second season onwards; however the vast majority of these have only the dubbed German soundtracks. (Amongst these does remain an English-tracked edition not held by the BBC, A Family Affair (1971)). To further muddy the waters, some German prints feature alternative footage which UK viewers never saw, and vice versa. Such differences even extend to the credits (the German prints retain the John Levene "running man" credit sequence even on later episodes where it had been supplanted in the UK originals). A monochrome 16mm copy of Murder in Munich: Part 1 (1970) (with original English soundtrack) was eBayed to a private bidder in July 2023.
There were several differences of opinion between the BBC and the Munich-based backers. The Germans were very keen on Ros Drinkwater as Steve (the BBC were reportedly less sure of her) and wanted to toughen up the stories, increase the action sequences and make the Temples appear more affluent. This 'interference' may have led to the show's demise.
Francis Matthews was Durbridge's first choice for the lead rôle, having worked with him in the past.
This was the first series the BBC made as an international co-production. UK prints credit Taurus Films as co-producers, whilst the German version refer to ZDF (Zweites Deutsches Fernsehen). This was very much due to creator Francis Durbridge's popularity in Germany (the author himself didn't write for the show but his 1970 books "The Harkdale Robbery" and "The Kelby Affair" were seemingly devised for it) and allowed the series to venture overseas and widen its casting base. The videotape masters were copied onto colour film to air in Germany.