It's got difficult for me to walk down the street without people stopping me to ask for an autograph or to talk to me about boxing.

If I've done a gig and at the end there are people waiting for autographs, they always seem nervous, but they probably don't realise that I'm more nervous than them. I get very embarrassed.

Signing autographs is weird. I'm an introvert, so it's been a strain in that way.

I remember, once I was going through Nice airport with Roger Moore, and these kids came up and asked for our autographs. Afterwards, Roger said, 'It must be very strange for you. I'm an actor, and signing autographs is part of what I do. But you're a public figure who people don't really know.' He was right.

This mum comes up, she's got a five-year-old kid and she says, 'Can he have your autograph, you are his favourite person in the whole world.' I thought, 'How cool is that? I've got five-year-old fans,' and as I'm signing this autograph, the mum goes, 'Yeah, yeah, you're by far the best Wiggle.'

It's never a good idea for a celebrity to sign autographs or take pictures if a crowd is gathering.

Now, as an astronaut, I have to bring a Sharpie with me everywhere - so I have a pen to sign autographs.