HOWZAT

“There is this huge constituency of people who are curious about the world,” he says. “It was great to hear from people saying ‘I hated maths at school but I loved your book’.” In the wake of books such as Fermat and Longitude, popular science became a growth genre. “I tried to do what I had done when making TV — to tell a story and to explain some science,” he says. “When you make telly, you bear in mind that there is a wide audience, without a background in science, so you make the programme gripping and explain the science clearly.

“I did not want my readers to become frustrated with the mathematics. My general plan was to tell the story and sprinkle the maths along the way. The great thing about Fermat’s Last Theorem is that it has a beginning, a middle and an end, and a plot twist, and heroes and villains. But you have to include the concepts. I want readers to have that ‘Ah! moment’, when they suddenly realise why prime numbers are so important or why there must be an infinite number of primes or what a proof by contradiction is.”

And fame? He dismisses it with a nod to a video of The Office. “I’m not Ricky Gervais; most people don’t know who I am. But, as a massive Queen fan, it was great to hear Brian May had bought a copy.”

Given the success of Fermat and his next opus, The Code Book (2000), it comes as a shock when he reveals his third will also be his final book. “And that will be news to my agent too,” he laughs. “But it’s time to do something else.”

It will be the story of cosmology. “When my grandfather was born no one knew where the Universe came from and now in a couple of generations we are at the stage where scientists can talk of the Big Bang. I think that’s absolutely gobsmacking. But writing takes so much out of your life. I’m not sure whether books are the best way to communicate ideas, compared to TV or teaching. I want to do other things, other projects.”

Singh is a man with a mission. Disgusted at the lack of qualified teachers in many schools, he is overseeing a scheme placing maths and science graduates in schools to teach “and act as role models and inspiration” to pupils.

“I’ve got the time and some clout now,” he says. “Successive governments have done the shoddiest job imaginable in getting science teachers into classrooms. The numeracy strategy is doing well and some parts of the primary school maths curriculum are working, but it must be fairer. Here’s an opportunity for the Education Minister to prove himself.”

He is genuinely angry. “If you get a degree in science, you get hoiked off into the dot-com industry or software development. Being a science teacher is the best job in the world, but if you’re being overworked, disrespected and getting better job offers, what are you going to do?” Singh’s advocacy is all-consuming. “Maths and science are beautiful. They are part of our culture, like music, poetry or theatre. Also, we need scientists and mathematicians to help to energise the economy. If we do not have enough computer scientists, engineers, geneticists and inventors, UK plc goes down the plughole.

“Most importantly, our lives are increasingly influenced by scientific and technological issues. In an age when there will be difficult decisions to be made about issues like cloning and stem cells, we need to be informed. Otherwise, as a society, we’ll make stupid decisions.” He is angry that parents rejected the majority scientific view of the MMR jab — that it was safe. But he can’t be surprised, I say, that there is a mistrust of science given its perceived loftiness and abuses.

“Science cannot be the absolute authority on anything,” he replies, “but at the end of the day the scientific, rational approach to giving an answer is better than the emotional, anecdotal approach. Science is not perfect, but it’s the best type of unbiased knowledge we have.”

IS it all work with Singh? His living-room is essentially an office, with few personal possessions. Shelves are stacked with box files, books for research and the odd video (The Office, Scream, Alan Partridge). He is, he says, socially phobic, turning down invitations to parties and only comfortable one-on-one with close friends. Yes, he assents, that is odd considering how comfortable he is on stage or in front of the camera.

He is 38 and unmarried, though he has been in love. “I am ready to settle down and have a wife and children,” he says quietly. “The challenge for me is to find the right person. I just don’t understand how people have both a home life and work life. I just don’t know it would work. But it would. If I had a family, I would want it to be like my own childhood. Growing up in Somerset in a small town, a rural community, people living near each other, kids staying up late to play football. I’m ready for it now.”