Sometimes restoration is tricky, [archivist] Mr [Dick] Fiddy says, picking a programme being screened on Saturday as an example.
"Out of the Trees was a pilot - intended to go to a series - written by Douglas Adams and Graham Chapman, starring many of the people that would go on to be in the Hitchhiker's Guide to the Galaxy.
"It went out, but was junked almost immediately afterwards.
"It had been recorded by Chapman at home on a very old-fashioned, primitive video machine.
"Recently, his long-term partner, David Sherlock, mentioned to me that he had this old tape, and could we play it."
It took two years to transfer because a customised player had to be built, Mr Fiddy says, with the entire process filmed in case the tape "dissolves after one play".
Friday, December 01, 2006
Kevin Young, for BBC News, reveals how 'lost TV classics' are tracked down by archivists at London's National Film Theatre.