London (CNN) -- For years the practice by television companies during the 1960s of erasing videotapes containing original episodes of classic shows has frustrated fans. But every so often, a long-lost treasure is found in an attic or at the back of a garage to revive their faith.
Now it's the turn of devotees of the time-travelling alien adventure TV show "Doctor Who," who were on Monday enthusing on Twitter about the discovery of two episodes that were believed to have been wiped long ago.
Tapes of the two BBC shows, "Galaxy 4 part three" starring William Hartnell and "The Underwater Menace part two" with Patrick Troughton, were bought at a school fete by former TV engineer Terry Burnett in the 1980s. He kept them at home for many years, and was only recently alerted to the fact that the BBC did not own them.
The footage was shown at the British Film Institute's annual "Missing Believed Wiped" event at the National Film Theatre in London hosted by actor Mark Gatiss. He said: "Christmas has come early for Doctor Who fans everywhere," according to the Radio Times.
"It's always wonderful when a missing episode turns up but it's been years since the last one so to have two is just brilliant. Add to that a proper bit of action from the legendary Chumblies (and the horrifying Rills!) plus the utterly mesmeric Patrick Troughton on great form. Well, what more could we all ask for?"
On Twitter, fans were similarly euphoric about the rediscovered episodes, which date from the mid-60s. JP LeBreton said: "Recovering lost Dr Who eps that broadcast 47 years ago and bounced off stuff in deep space: coolest thing possible."
Broadcasters started to record TV programs for transmission in the late 1950s, but because videotape was so expensive, they were wiped clean for reuse afterwards. Because of this more than 100 episodes of "Doctor Who" from the 1960s were lost. The latest discoveries are the first complete episodes to be rediscovered since 2004.
Details of any commercial release for the rediscovered episodes will be announced next year.