Image caption The Beatles' shows in 1965 rarely lasted longer than 40 minutes

The Beatles showed their support for the US civil rights movement by refusing to play in front of segregated audiences, a contract shows.

The document, which is to be auctioned next week, relates a 1965 concert at the Cow Palace in California.

Signed by manager Brian Epstein, it specifies that The Beatles "not be required to perform in front of a segregated audience".

The agreement also guarantees the band payment of $40,000 (£25,338).

Other requirements include a special drumming platform for Ringo Starr and the provision of 150 uniformed police officers for protection.

But the security arrangements were not perfect.

The band played two sets, a matinee and an evening performance, at the venue on 31 August, 1965. At the latter, some of the 17,000-strong crowd broke through security barriers and rushed the stage.

The show was halted, and The Beatles were forced to wait backstage while order was restored.

They eventually finished their 12-song set with Help! followed by its B-side, I'm Down.

The Beatles had previously taken a public stand on civil rights in 1964, when they refused to perform at a segregated concert at the Gator Bowl in Jacksonville, Florida.

City officials relented, allowing the stadium to be integrated, and the band took to the stage.

"We never play to segregated audiences and we aren't going to start now," said John Lennon. "I'd sooner lose our appearance money."

The struggle for racial equality in America later inspired Paul McCartney to write Blackbird.

The contract for The Beatles' 1965 show is expected to raise up to $5,000 (£3,167) when it goes up for sale by a specialist memorabilia auctioneer in Los Angeles on 20 September.