Sir Paul McCartney never tires of performing Beatles hits like Yesterday and Blackbird because he always wants to perfect them and understand what was going on in his mind when he wrote the songs.

The singer/songwriter admits he thought he'd be sick of his old hits by now, but he still enjoys belting them out onstage.

He explains, "What it is, is I'm actually trying to play the song like I know it effortlessly, but there is a pattern I must not miss, and there are words I must put with that pattern, so I'm normally still trying to get it right.

"And what I find myself doing is re-examining the work of this twentysomething. It's like it's not mine. It's not a dawdle. There's hardly anything where I switch to autopilot. Instead of being bored with a song, I'm still trying to look at it: 'What the hell is this thing?'"