Sir Paul McCartney has explained his embarrassing performance gaffe during the London Olympics Opening ceremony, revealing he made a big mistake and missed his cue.

The Beatles legend was among the high-profile acts chosen to perform for billions of viewers at Danny Boyle's spectacular show to mark the launch of the 2012 games in the British capital in July (12).

MCCartney was given the special privilege of closing the ceremony at London's Olympic Stadium, but he was left red-faced when he started singing hit Hey Jude at the wrong moment and fell out of time with his pre-recorded vocals and backing track.

He has now explained the mix-up, revealing he was distracted by the ringing of a giant bell in the stadium.

MCCartney tells Britain's NME magazine, "I f**ked up. I was supposed to wait for a cue. But I forgot. Why? Well, there's this bloody great bell that we didn't know about. It was deafening... We prerecorded a playback in case all hell broke loose... We were live, everyone was there, the world was ready and this bloody great bell goes off. And I forget I've gotta wait for it, so I go, 'Hey Jude', and someone presses the playback. So there's me on the backing track, and actual me; two of us singing. The drummer wouldn't look at me because he was in hysterics and I was thinking, 'What have I done?' There was no stopping, it was the Olympics."