Several editions of this series were destroyed as late as the early 1990's.
In fact, the most recent notorious BBC Childrens programme archive purge happen in the early 1990s, in addition to the infamous legacy archiving of either never recording a show, or wiping the expensive video tapes for re-use, pre-1978, that most other global broadcasters did too. Apparently, its said that the head of the BBC (video) Archive at the time, Adam Lee, decided to "prune back" the Children's archive as he deemed it "of little use", and went ahead junking possibly thousands of their archive programmes, seemingly without consulting the actual Children's Programme Department. In turn the Children's Department only discovered this, as they were actually considering re-using parts of the legacy Archive within new programming schedules as extracts and/or re-running classic shows, and wanted to review the old tapes, which no longer existed for many shows, beyond what they already knew had already been lost pre-1978.