Former Beatles Sir Paul McCartney and Ringo Starr reunited for a walk down memory lane on Thursday for the premiere of a documentary by Oscar winner Ron Howard about the Fab Four as they toured the world in the 1960s.

The singer-songwriter and drummer posed for photographs on a blue carpet in London's Leicester Square for the "The Beatles: Eight Days a Week - The Touring Years" premiere, which drew hundreds of cheering fans as well as celebrities such as Madonna, Eric Clapton, Bob Geldof and Liam Gallagher.

The documentary traces the band's touring years as McCartney, Starr along with the late John Lennon and George Harrison won legions of adoring fans across continents. It features footage of early performances at the Cavern Club in their native Liverpool, packed shows around the globe and their final tour concert in 1966 in San Francisco.

"We're all excited, it is the first time for us too," Starr told the crowd about seeing the documentary.

The film makes use of a rich archive of old footage - pictures, videos and audio recordings - of the band at the height of Beatlemania, with screaming fans, snippets of the cheekiness of the then young men and the group at work in the studio. Celebrities recalling seeing them perform also add their voices.

"We started off as four mates in a great little band and we kept playing and playing and all this stuff happened," McCartney said.

Howard said that as well as receiving help from McCartney and Starr for the film, Lennon's and Harrison's widows, Yoko Ono and Olivia Harrison, who attended the premiere, had also contributed to the project.

The director, known for films such as "The Da Vinci Code", "A Beautiful Mind" and "Apollo 13", said directing the documentary had been "a great experience".

"It first began as just a fun, cool, creative adventure, then I became very intimidated by it when I realized how important it was to fans," he told reporters.

"Now it's just proved to be a very gratifying experience, and I'm already nostalgic for it ... After two years of working with it, I'm a little sad to let it go."

"The Beatles: Eight Days a Week - The Touring Years" hit cinemas worldwide on Thursday.