Lost Beach Boys lyrics, music and photographs expected to sell for $10m after lying in Florida storage unit for years Handwritten songs and scores, plus unseen photographs, for sale in London Archive of memorabilia lay in Florida storage depot til it was bought blind Includes handwritten music for hits including Surfin USA and California Girls The Beach Boys treasure trove which lay in a Florida storage unit for years includes photographs, lyrics and music, and is expected to sell for $10m A 'lost' archive of original music manuscripts by the Beach Boys for 150 of their songs has emerged for sale for nearly £7m. The vast collection spanning the first 20 years of the band's hugely successful career, lay forgotten in a storage unit before it was found and put up for auction. The treasure trove includes original, hand-written musical arrangements for hits like Surfin USA , God Only Knows, California Girls and I Get Around. There is printed sheet music for other classics like Good Vibrations, Fun, Fun, Fun and Don't Worry Baby. It also includes handwritten lyrics, recording contracts and copyright certificates signed by Brian Wilson and Mike Love, royalty cheques and personal letters. And there are more than 60 behind-the-scenes photos of the hugely successful American rock band, many of which have never been seen before. The documents, which will go on show in London next week, are all original and were mostly created in the 1960s. The archive is being sold as a single lot and has been billed as one of the most important ever auctions of pop memorabilia. Incredibly, it was only discovered by chance when a small company dealing in music promotion took part in a 'lucky dip' blind auction at a lock-up facility in Florida, US. The storage unit contents which originally sold for just a few hundred dollars contain original lyrics and scores They were then astonished to discover that the few hundred dollars they had gambled on the lock-up contents had bought them original music, lyrics and photographs worth millions of dollars. It is believed the material had been placed there for safe-keeping by an associate of the band in the late 1970s and then simply forgotten about. Its emergence led to a legal dispute which has since been settled after it was ruled it had been a 'fair find'. The surviving members of the Beach Boys are aware of the sale. The archive is being sold by British auctioneers the Fame Bureau in a sealed bid auction. Ted Owen, of the Fame Bureau, said: 'This archive is like the Bible of the Beach Boys career. It is so vast, it would take six months to catalogue. Among the crate's contents was the original studio arrangement for the Beach Boys' hit Surfin' USA It is the largest archive of modern musical history that will ever likely be offered for sale from a group of musicians and genius songwriters that influenced the world. It covers 150 songs from the early development of the Beach Boys to their comeback of 1976. The majority of the songs include hand-written scores, publishing and copyright contracts and compositions for artist participation of drums, bass and strings. There will never be an archive like this ever again. Only the Beatles or the Rolling Stones would have this body of work but they are never going to come to light. Up for sale are the original studio arrangements for I Get Around, left, and the handwritten lyrics for Ain't It Sad This sale has really come about by accident. The archive was lost over the course of time and was really found by chance. It was a blind storage unit sale and the items inside were listed as documents and books. A small company of music promoters took a gamble on it and bought the contents for a few hundred pounds. 'It didn't take them long to figure out what they had but it has taken some time to put a value on it. Photographs, many unseen, show the Beach Boys' private side - here Brian Wilson is seen at the mixing desk The photos show the stars off-duty and relaxed - this image, dating back to the mid-1960s, is of the band in Rome Of course it is the Beach Boys property and its discovery led to a protracted legal dispute which resulted in it being labelled a fair find. Alan Boyd, the Beach Boys official archivist, said: 'This historic collection presents a priceless look into the inner workings of this legendary group. 'When these documents were created in the 1960s and '70s, there was no thought they would someday tell an important part of the story of one of the most impressive - not to mention lucrative - catalogues in the history of popular music.' The lost archive (this image shows the band in London in the late 1960s) is expected to sell for $10m The Beach Boys, from California, formed in 1961 and were made up of brothers Brian, Dennis and Carl Wilson, their cousin Mike Love and friend Al Jardine. They have sold more then 350 million records around the world and had 25 number one hits. Of the original line-up, drummer Dennis Wilson tragically drowned in 1983 aged 39 and brother Carl died of cancer in 1998. The archive will be displayed in New York on April 15 and at London's Hard Rock Cafe on April 18. The deadline for the sealed bids for the auction is May 15.