London, Jan. 19 (Reuters): If rock and roll fans could conjure up their dream recording date, it might be a jam session between Beatle John Lennon and Rolling Stone Mick Jagger.

A record collector in London says he has found just that — and will be offering the previously unknown recording at an auction next month.

Tom Fisher said on Saturday he had bought the unmarked record from another collector. When he listened to it, he was convinced it was Jagger on vocals, singing a raucous old blues song called Too Many Cooks.

Auction house Cooper Owen says Lennon is part of the backup band.