From the moment you first meet Derren Brown he exudes a warmth and charisma that commands your attention entirely. This is the man who has been described as the "scariest man in Britain" and as possessing a "witch’s heart", but when I meet him he is dressed casually in a shirt and purple pullover, sipping liquorice tea. He asks a bit about Varsity and I pull out a copy of last week’s issue to show him; "It’s better than Bristol’s," he announces, impressed, "ours was called Epigram and it was rubbish."

I ask what his overall memories were of university. "I think I was a bit of a dick. I used to wear extraordinarily colourful, gaudy clothes and was horrible – I don’t think I’d have liked me at all. When I started performing it took care of all that: I’m still wearing [looks at colourful jumper he is wearing] but I became much quieter in my ordinary life because all that desire for attention now had a bona fide outlet." When pressed to define exactly what it is that he does, Brown pauses, "I don’t know what label to put on it other than doing what I enjoy... I do wonder why I do it and what the point of it is. Ultimately I just have to settle with the perfectly good, healthy, and worthwhile reason that entertaining people is a fine end and there doesn’t have to be anything more noble than that. Beyond that, if they enjoy it and it makes them think a little bit about what they believe then that is very satisfying."

The Events, his recent four-part series on Channel 4 opened with his famous prediction of the National Lottery. He is surprisingly modest about this feat. "It was never an aim for it to be a big publicity stunt; Channel 4 decided to make a big thing about it. The idea of me predicting the National Lottery sounds like a major thing, but it really wasn’t. I was just trying to think of a good idea for the first of a series of four specials which would have appealed and attracted the same people who watch the shows anyway. But Channel 4 said, ‘This has the potential to be huge,’ and really went for it, which is fantastic but slightly daunting."

Brown has been criticised by some individuals for misleading his audiences about how he has achieved certain effects. He responds to my question about how much these explanations are divulging the truth and how much they are enhancing the effect, saying, "It is always to enhance the effect; there is only the effect... I’ll explain something if the explanation is at least as entertaining as the trick, I won’t simply explain." What about the Friday night show which purported to explain how he had predicted the Lottery? "That was written and conceived months before we knew it was going to be this huge hit and [it was expected that] the people that would be watching it on the Friday would be people who ‘got me’ and knew that I wasn’t really going to stand there and say how it was done. So there was this whole sort of ambiguity and false trails thing of wisdom of crowds and then me saying at the end, ‘well you don’t have to believe that’. That sort of got missed by people who wouldn’t normally watch my show."

Another side of Brown’s work is his underlying scepticism about unsubstantiated belief, especially with regard to religion. He recalls how his scepticism of his own faith developed while he was at university, at the same time as forging a passion for magic and hypnotism. When I enquire whether these changes were interrelated, he responds affirmatively: "Yes, definitely. The interest in hypnosis came first and what I got from that was an interest in magic and the general scepticism that comes from that, and I got a general sense of how easily people could be fooled." Yet Brown is no militant atheist; it is clear he has both a respect for and an interest in the beliefs of others: "I consider myself as an atheist (that I don’t believe) in the same way that I don’t happen to collect stamps and don’t happen to do a number of other things. I don’t have the same vehemence for it [religion] but I don’t consider myself an ‘anti-theist." Does he think there is a role for faith in the world? "There are many different embodiments of faith and some of them are socially repulsive and some are perfectly socially pleasant. I think that what is a very good reason for believing in something is that it might genuinely make somebody happier and they might take a huge amount of comfort from it. My concern is the obvious thing: whether people are hurting or upsetting other people."

This exemplifies Brown’s entire approach, a balance between "scepticism but at the same time a love of wanting it to be true," all behind a respectful, friendly, and funny persona.

I ask Brown whether he experienced any reaction to the news he was gay – something he revealed in The Independent in 2007, "No, I think it is one of those odd things. I guess most people, myself included, big it up in your mind as this big awful hurdle that at some point you have to deal with and then when you do no one cares."

Our time is nearly up and Brown is required on stage. He waits for me to wrap up the interview before thanking me and giving me a ticket to see the night’s performance. It is rare for a person to live up to their fans’ expectations when they are met in the flesh; it is even rarer for a person to surpass this expectation. As I leave Brown doing a soundcheck on stage, I reflect on the sheer diversity of his character: mentalist, magician, psychologist, rationalist, comic but perhaps most importantly, and most often overlooked, a genuinely nice man trying to give people a good time.