Got back: 500 'priceless' Beatles tapes, stolen 30 years ago in rock 'n' roll's greatest robbery

One of the biggest mysteries of pop was solved yesterday when police and music industry chiefs announced the retrieval of the legendary "Get Back" tapes made of the Beatles in 1969 – shortly before their break-up.

The 500 rolls of reel-to-reel tape, which capture every song, including endless retakes, false starts, musical doodlings, arguments and chat between the Fab Four and their producer George Martin, were recorded by the filmmaker Michael Lindsay-Hogg in London in January 1969 but went missing sometime later.

The rehearsal and recording sessions later formed the basis for the Let It Be album and film. The tapes were rescued yesterday after raids in South-east England and the Netherlands after an inquiry by the International Federation of the Phonographic Industry (IFPI) and the British Phonographic Industry. Six people were arrested.

Recorded at a crucial time for the group, when tensions were tearing them apart, the tapes have long been of immense interest to Beatles enthusiasts.

"This was probably the most significant theft in rock and roll, because, without doubt, these are irreplaceable artefacts in the history of popular music,'' said Michael Ellis, head of western European investigations for the IFPI.

They were discovered missing sometime in the early 1970s but it was not until 20 years later that a sequence of bootleg CDs began appearing. Each bore dates of the various sessions, which took place almost every day during January 1969 and culminated in the famous performance on the roof of the Apple building in Saville Row, central London, on the 30th.

Yesterday's arrests came as a consequence of a lucky find a few months ago when, in the course of another inquiry, investigators found a large number of bootlegs and began to track down the source. The sessions include Yoko Ono's involvement, Billy Preston playing on drums and an argument with John Lennon after which George Harrison quits. Many of the songs played are versions of those that appeared on the Let It Be album, such as "The Long and Winding Road", those already released, such as "Back in the USSR" and rock and roll standards, including "Hi Heel Sneakers" and "Little Queenie".

Mr Ellis said: "Its like plunging yourself into the studio: you can hear them taking off coats, tuning up, chatting, Paul asking for a sandwich, that sort of thing.''