Keith Richards said the Rolling Stones were relieved to reunite.

The band celebrate their 50th anniversary this year with a greatest hits album, GRRR!.

It is their first time working together since the A Bigger Bang tour ended in 2007.

Speaking to BBC Radio 6 Music, Keith said: ''We needed some time off. What I've noticed with this band this year, rehearsing over the last few months, and putting together Doom and Gloom and a couple of other tracks, is that there's almost a sigh of relief to get back to work.''

''This is what we do. The energy is certainly there. It's almost like, open the cage and let the tiger out. This is bottled up energy ready to go. That's the way I'm feeling about it and I think the rest of the band, too.''

The Rolling Stones' greatest hits album, GRRR!, is out now.