A handwritten letter from Paul McCartney on August 12, 1960 inviting an unnamed drummer to audition for a place in the Beatles has sold at Christie's for 34,850 pounds ($55,000).

The document was discovered folded up in a book purchased at a car boot sale in Liverpool, birthplace of the Fab Four.

It had been expected to fetch 7-9,000 pounds at a rock and pop memorabilia sale at Christie's in London late on Tuesday.

Shortly after the letter was written, the newly formed Beatles travelled to Hamburg, Germany, to play a series of gigs as they set out on the road to superstardom.

According to online Beatles timelines, drummer Pete Best joined the Beatles on August 12. He was thrown out of the band two years later and replaced by Ringo Starr.

The auctioneer said the letter was one of the earliest examples of the band being referred to as the Beatles.

It was also important to pop historians because it suggested McCartney was seeking an alternative to Best until the last minute and knew more about the details of the Hamburg trip than previously thought.

The top lot of the sale, fetching 97,250 pounds, was a hand-written sign reading BED PEACE displayed during one of John Lennon and Yoko Ono's famous bed-ins for peace in 1969.

Overall the auction fetched around 480,000 pounds.