''I don't play it up at all,'' he says. ''If you look at the programs, I just wander around looking a complete mess.''

In person he's anything but a complete mess. He's all loose-limbed energy, good hair and blindingly white teeth. But he'd much rather talk about his passion for communicating science than his reputation as this generation of women's Melvyn Bragg.

In his day job, away from all the popular books and the TV and radio shows, Cox does some very big science. Among other commitments, he is a Royal Society university research fellow at the University of Manchester and works on the Large Hadron Collider in Switzerland.

But aside from his intellect and appearance, he has built a reputation on the ability to explain hideously complex concepts and make the readers/viewers/listeners feel that maybe this science stuff is not beyond them after all.

''Science is the process by which we understand the natural world and it's nothing more complicated than saying, 'If you want to know how something works then look at it first, take some measurements and then try and understand those measurements,''' he says.

''That's really all it is and the key is to explain that.

''I believe science is too important not to be part of pop culture. It is the foundation of our society and therefore everybody should know something about it … I think we underestimate audiences.''

All this is delivered in his trademark soft Lancastrian accent, a legacy from growing up in Oldham and his continuing association with the north of England. He recalls an idyllic childhood, doing all the things youngsters did in the 1970s and '80s - playing football, riding his bike and bus spotting.

Er, bus spotting?

''For a while I had a book detailing all the serial numbers of all the buses in Greater Manchester and I used to tick them off when I saw them,'' he says. ''I was geeky in a way but quite normal. I was also interested in astronomy and planes.''

Then at age 15 he became interested in pop music.

''I wanted to be a pop star so I taught myself how to play piano but only in order to become a pop star,'' he says. ''It was quite specific and logical.''

Somewhat improbably, he succeeded in his ambitions, initially with the rock band Dare and then D:Ream, who were among the most successful English bands of the mid-1990s.

Eventually science reclaimed him from pop music. He began popping up on television, first as a commentator and then, increasingly, as the main act, explaining his work and that of others.

He has been credited in part with the recent explosion in enrolments in British science courses at both high school and undergraduate level, a trend Cox would like to see reach the highest levels.

''Science is becoming more popular,'' he says. ''It's quite cool to be rational now and I think politicians pick up on that and worry about being attacked on the basis they are ignoring the science.

''They shouldn't, as sometimes happens, say, 'Well, I don't believe it.' You're not allowed to say that but you are allowed to say, 'I took account of that but there are other pressures and I've weighed them all and come to a decision.'''

As well as his job as science evangelist, Cox has in recent years also been cast in the role of celebrity atheist, a position he is not entirely comfortable with (''If I'm going to be defined by what I don't believe in we're going to be here all day!'').

However, he admits he has tackled the topic in the just-written introduction to his latest book, Wonders of Life, a broad look at natural history and evolution, which accompanies the TV series of the same name.

And even as an avowed non-believer, he sees no reason why science and belief cannot coexist.

''I see no necessary contradiction between the two, particularly if you are a deist,'' he says.

''You can't believe the Earth is 6000 years old. That is just drivel.

''But you can have some faith and believe this is all too wonderful to be here by chance and also appreciate the beauty of science. I want those people to watch my programs and if it reinforces their faith because it is so beautiful then that's fine by me.

''What isn't fine by me by a long way is teaching kids that evolution didn't happen.

''Then it becomes dangerous.''

Wonders of Life by Brian Cox will be published by HarperCollins in February.