An 11-second clip of the Beatles' only live appearance on Top of the Pops, which was thought to have been be lost, has been unearthed in Mexico.
The silent snippet is all that exists of the Fab Four miming to Paperback Writer on the BBC pop show in 1966.
The original tapes were not kept, but it was recorded by a viewer filming their TV set with an 8mm camera.
The footage was shot by a family in Liverpool and eventually fell into the hands of a collector in Mexico.
The collector contacted Kaleidoscope, a Birmingham-based organisation specialising in locating previously missing TV footage.
"I think if you're a Beatles fans, it's the holy grail," Kaleidoscope's Chris Perry told BBC entertainment correspondent Colin Paterson.
"People thought it was gone forever because videotape wasn't kept in 1966. To find it all these years later was stunning."
The band pre-recorded songs for Top of the Pops on several occasions, but only appeared live once, on 16 June 1966. The performance itself has long-been a talking point for Beatles obsessives.
In 2000, a BBC spokeswoman said: "We don't know whether or not this particular piece of Top of the Pops history has disappeared forever, but unfortunately there was a time when BBC programmes were not archived as carefully as they are today and some programmes were sadly lost."
The rediscovered clip will be screened at the BFI in London as part of the Music Believed Wiped programme on 20 April.
Speaking about the discovery, Dr Dori Howard, a lecturer in The Beatles and Popular Music at Liverpool Hope University, said: "It's crazy, what are the chances? I would say it's a really big find."
A missing episode of Top of the Pops from 1969, featuring an early cut of The Beatles' promotional video for their single Something, has also been discovered.
The Beatles famously never toured again after playing live at their last ever gig at San Francisco's Candlestick Park in 1966, at the height of Beatlemania.
They reunited for a one-off performance on the rooftop of Apple Records in London in 1969.
The Music Believed Wiped screening will include highlights of 240 musical performances that have recently been found by Kaleidoscope.
They include Elton John singing Rocket Man on Top of the Pops in 1972, T Rex's fourth and final UK number one Metal Guru, and a pieced-together Slade performance from 1975.