So I don't when I'm sitting in the middle of Little Earth as Gandalf with all the beard and what not I'm not thinking about Magneto.
And when I'm doing magical things as the Master of Magnetism I'm not thinking about Gandalf so I don't make the connections.
And hopefully I look different on the screen, and sound a little bit different so the audience doesn't get confused either.
You've had this amazing career and in the last few years taken on roles children will associate with. Is this deliberate?
It's just the way things have worked out.
When I was very young I played David Copperfield on screen for 13 weeks on BBC television for kids and had a lot of young fans because of that so it's not entirely alien.
What is unusual is the very young age of some of Gandalf's fans - he's got five or six year-olds that have seen the film 20 or 30 times.
I take it as a compliment.
But I know in my heart of hearts that when that little five-year-old looks up at me and asks for my autograph, that basically what they're asking is Gandalf for his autograph but that's fine with me.
Is it a bit like what it was like for Alec Guinness and Star Wars?
I don't make good distinctions between being in a very, very popular movie and being in a play in the West End of London that a lot fewer people see. To me it's just work.
And actually I'm rather late in the day, enjoying doing two things at once.
At the moment I'm in a play in the West End of London - Dance of Death it's called - and at the same time 100 yards away in Leicester Square in London you can go and see LOTR and X-Men 2 and it's the same actor.
And that makes me feel nice and warm inside and it's something I've always wanted to do.
Would you have got involved with X-Men, playing what is essentially a comic book character if you hadn't already worked with Brian Singer before?
No - success as an actor, or getting on and getting parts that you really want to play, is not something you can easily manipulate yourself.