"I suspect we're not the only family in the country that likes to have a friendly row on Christmas Day," admits Jim Al-Khalili, sat in his office in the physics department at the University of Surrey. "I guarantee we will have the usual Al-Khalili religion debate. My wife gets very frustrated about it. It's the same old argument every year."

But this year might be a little more fraught than most. Mr Khalili's mother is still a devout, church-going Christian but, next week, her 40-year-old son will become the next president of the British Humanist Association, the ever-expanding organisation for, in its own words, "people who seek to live good lives without religious or superstitious beliefs".

"She felt somewhat disappointed that I had taken on this role," he admits. "I said: 'You shouldn't be. You shouldn't be any more disappointed than I am that you go to church every Sunday.'"

Mr Khalili, who grew up in Iraq with his Christian mother and his "bordering on agnostic Muslim" father, is a theoretical physicist and also presents The Life Scientific on Radio 4.

A scientist-atheist then – which makes comparisons with Professor Richard Dawkins inevitable. But Mr Khalili is keen to portray himself as more cuddly than the man dubbed "Darwin's Rottweiler". Cuddly?

"Yes. Cuddly. I am a cuddly atheist. Someone who doesn't feel the need to tell you that what you believe in is stupid. Take my mother, I will tell her: 'I'm happy for you, because I know your religious faith fills a hole in your life.' I can see how important it is to her to have this faith. What right do I have to destroy it?

"I'd like to see her one day say: 'You know, I don't think God exists,' but I'm not going to be arguing and pushing that she is wrong.

"I am against creationism being taught in schools because there is empirical evidence that it is a silly notion, but I don't put religious faith in that bracket. I have no evidence to prove there is no God. The burden of proof is on them, yes, but I don't force it upon them to prove it. If they want to have a religious faith that is up to them. I won't dictate to them.

"I'm not going to have a debate with someone whose religious faith is very important to them and expect them to say: 'Ah, of course, you're right. There is no God.' It's not going to happen. If people turn away from religion it is because they see there is no need in their worldview for a supernatural being guiding how they live their lives."