An unheard song penned by Sir Paul McCartney and Sir Ringo Starr is expected to be sold for around £20,000 at auction.

The song, called 'Angel in Disguise', was written during the recording sessions for Ringo's 1992 album 'Time Takes Time', although it didn't make the final cut.

The unheard record appears on a cassette tape, which is part of British DJ Tony Prince's collection.

The lot description explains that there are two versions of the song on the tape, with the first rendition featuring McCartney singing the lyrics over a piano and drum machine.

The second version, on the other hand, features ''a full backing track, backing singers, increased instrumentation including harmonica, guitar and more''.

The tape has been put up for online auction through Omega Auctions, and has been given an estimated price of £10,000 to £20,000.

Last month, meanwhile, McCartney's handwritten lyrics for 'Hey Jude' sold for $910,000 at auction.

The iconic song - which was released in August 1968 - is one of the Beatles' most popular singles, and according to auction house Julien's Auctions, the lyrics sold for nine times its original estimate in an online auction.

Speaking prior to the sale, Julien's Auctions music specialist Jason Watkins said: ''It's obviously a very iconic song that everyone's familiar with.

''These handwritten lyrics were used in the studio as a guide when they were recording it.''

Elsewhere, a drawing by John Lennon and his wife Yoko Ono called 'Bagism' sold for $93,750, while an ashtray used by Ringo at the Abbey Road recording studios in London was sold for $32,500.