Partly for contractual reasons, and partly because Oliver Postgate considers it below par, the one-off special hasn’t been seen since it was first aired in 1974. It’s being used in the documentary to illustrate a section on the increasing politicisation of children’s television during that decade, but although it will be nice to see some footage, it would be even better if BBC4 could see fit to give the entire show a long-overdue repeat.