Sir: That the final episode of Doctor Who's "The Tenth Planet" was lost after compilation of a 1973 episode of Blue Peter (letter, 12 October) is not quite true. BBC Enterprises was still marketing the complete "Tenth Planet" well into 1974.
However a second episode used in the same Blue Peter programme did go missing after the show. The episode, part of the epic William Hartnell tale "The Daleks' Masterplan" was signed out of the film library by a J Smith. Strangely enough, the false name used by the Doctor himself on the programme was John Smith.
Next month sees the 35th anniversary of Doctor Who and despite the amazing efforts of fans and archivists 110 episodes still remain missing. I hope the renewed interest helps to unearth some of these missing half hours. Maybe even the mysterious J Smith will step forward.