Stars' early appearances discovered
Early TV appearances by stars including Sean Connery, Maggie Smith and Derek Jacobi will be seen for the first time since they were originally transmitted after hours of footage was uncovered by accident.
An American researcher found the tapes in the Library of Congress in Washington DC and they have now been handed over to the British Film Institute (BFI).
BFI curator Steve Bryant said: "The BFI's "Missing, Believed Wiped" campaign to recover the lost treasures of British television history has been going for 17 years now, but this is by far the largest and most significant collection of programmes we have found, both in terms of the quality and the vintage of the titles concerned."
The lost footage dates from between 1957 to 1969.
The tapes belonged originally to Public Broadcasting Service WNET New York who broadcast them following UK transmission on BBC or ITV.
Selected highlights of the collection will be shown at the BFI's annual Missing Believed Wiped festival.