Daltrey, McCartney, and Wood backstage at Royal Albert Hall

Paul McCartney joined Rolling Stones guitarist Ronnie Wood and The Who's Roger Daltrey at London's Royal Albert Hall Thursday, for a rousing version of the Beatles' 1969 hit, 'Get Back'.  It's the second time Wood and McCartney have teamed up on the song in recent months.

The performance was part of a weeklong series of benefits for the Teenage Cancer Trust.

McCartney's sang 30 songs, including Jimi Hendrix's 'Foxy Lady' and 20 Beatles tunes. During the encore, he brought out Daltrey, Wood, and Paul Weller. Weller's new album, Sonic Kicks, recently debuted at No. 1 on the British album charts.  Weller played rhythm guitar, Wood got a solo, and Daltrey sang harmony.

The long 50th anniversary season -- celebrating the start of the British Invasion -- is getting underway. The Rolling Stones plan to mark their half century together with a documentary to be released in September. It will feature footage dating back to 1963, including film stashed in vaults and from personal collections.

Keith Richards

Earlier this week, Rolling Stone magazine confirmed the band has postponed its 50th anniversary tour until next year.  The magazine quotes Keith Richards as saying they're just not ready. But insiders say Richards' health is one reason for the delay. The guitarist was on vacation in Fiji in 2006 when he suffered a head injury from which he's never fully recovered.

Also planned to mark the Stones anniversary is release of an album of 700 photographs.