An original black and white version recorded on 13 November 1970 and never shown to the public it was withdrawn half way through production, it was then junked, it is not known to exist.This episode was replaced by a color version that was recorded on 27 May 1971 and aired on 10 October 1971. The original black and white episode was completed and broadcast in the UK, as it was made during the colour strike, where the TV unions refused to work with the new colour equipment. Several episodes were made in black and white because of this, which were excluded from overseas sales. The first episode, "On Trial", was remade in colour, with an altenate ending, to explain Sarah's absence in the colour episodes, before her return later in the series. The original black and white episode has only been repeated on UK TV once, when Channel 4 had a complete run in the mid-'80s. Subsequent repeats on ITV3 skipped the black and white episodes and used the remade "On Trial".