Children's television programme The Clangers was created in 1968 by Oliver Postgate and Peter Firmin.
The programme featured a group of creatures called Clangers who lived below their planet's surface in caves.
Author Michael Rosen and Professor Paul Wells explain how an episode of The Clangers from 1974 was a comment on the UK general election.
Time Shift: Oliver Postgate - A Life in Small Films will be broadcast on Tuesday, 22 December 2009 at 2000 BST on BBC Four. Or catch-up afterwards on BBC