Mother of three turned sex guru

To my huge relief, when we meet at her groovy office just off Oxford Street, Suzi Godson, author of a new manual that is already being called The Joy of Sex for the 21st century, is not wearing Jesus sandals, wooden beads or an itchy green cardigan - and neither does she peer at me over the top of half-moon spectacles. In fact, with her hipster jeans, bleached hair and scarlet lipstick, she looks like the kind of girl who would rather pop down Topshop than spend hours droning on about penile dysfunction (and other things I am too embarrassed to go into here).

But then, since she is not a sex therapist, perhaps this is to be expected. Some years ago, Godson, a designer, began writing a sex column for a Sunday broadsheet. The size of her postbag convinced her she should do a book - one that definitely would not include any pictures of men with facial hair. "No," she snorts (if she thinks you're being mischievous or at all Benny Hill, Ms Godson can get quite cross). "You won't find any beards in my book. And The Joy of Sex is so focused on penetration. I wanted to write about sex in a way that wasn't creepy or salacious."

The result is The Sex Book, a satisfyingly thick volume which aims to do for your bedroom what a Jamie Oliver or Nigella Lawson may already have done for your kitchen. It has a brightpink cover and, inside, is full of (quite) tasteful pop art-style illustrations, lots of spicy ideas and factual information on every subject under the sun, from latex to love bites, massage to the missionary position, pelvic floors to prostate glands. It is aimed at both sexes. "As a contribution to human happiness, this book deserves the widest possible readership," says Professor Robert Winston grandly, in his foreword.

Godson, who has been married for 14 years and has three daughters under the age of 10, grew up in Ireland where, from the age of eight, she attended a convent boarding school. "It was run by nuns and nobody told us a goddam thing," she says. "Trying to find out about sex was a nightmare. You did it by trial and error - a lot of error."

After school, she came to London, where she was a student at St Martins College of Art. "Like many young women, I had a lot of experiences that I didn't need or know how to negotiate. I had no confidence. I was very focused on pleasing my partner."

To research her book, she set up a webpage with links to 50 major sex websites, and posted questions on it. She also drew on a team of experts: doctors, therapists, rent boys, prostitutes. So which of her discoveries surprised her the most? "I found out that it is possible to have surgery on your labia on the NHS, under the extreme distress category. When I wrote about this in a column, I got an email from a woman who was 38 and had only had sex twice because she was so embarrassed by the way she looked. It's amazing, being able to point people in the right direction."

More generally, she was able to demolish a few of her own - and other people's - preconceived ideas. "I thought of men as being physical rather than emotional, but I came to see that intimacy is just as important for them as it is for some women, and that they really love it when a woman likes having sex. Similarly, I found that there are a lot of women who actively want emotion-free, commitment-free sex. Post-Pill sex is about recreation. It's taken women 40 years to catch on that it's supposed to be fun."

If a doctor attends a dinner party, I say, he or she usually gets asked to look at the other guests' suspicious lumps. Does Godwin have the same kind of trouble? "Er, no. I suppose people are more open when I'm around than they might be otherwise." Her husband, she says, has been supportive (though, presumably to avoid embarrassing him, she won't tell me his name or what he does for a living); her daughters are still too young to know what their mother gets up to in the privacy of her own office. "But, to be honest, when my kids get to 16, this is exactly the sort of thing I'd want them to read."

Of course, anyone who is reading this on a train after a long day at the office will no doubt feel that they are about as likely to go home and cover their partner with chocolate body paint as they are to rustle up Nigella's passion-fruit pavlova or Jamie's chicken-liver pat?. This bug-eyed, exhausted feeling is one that Godson understands - but she urges lovers everywhere not to become too reliant on the sexual equivalent of a nightly helping of beans on toast or a Marks and Sparks microwave meal.

"We're much more complacent about sex in relationships than we are about other things," she says. "We have to invest in everything else to keep it going but we don't work at sex. I'm thinking about quality, not quantity. If you don't have sex very often, then make sure that when you do, it is really good. A hotel is a wonderful, neutral space. Treat it like a date: book dinner, organise champagne for the room and ... wow! There's no way you're going to leave without having had sex."

The Sex Book is to be translated into a dozen languages and Godson has already been inundated with media requests (she did Ruby Wax's daytime television show last week, with Lulu). She could, if she fancied it, become the new, less wrinkly Dr Ruth, famous across the globe for her wise counsel and saucy anecdotes. But no, Suzi thinks not. For her, this is just another project, now completed. Anyway, she doesn't think sex works on TV. "The minute a couple say they are happy to talk about sex on telly, or have sex in front of a camera, you tend to think, right, I don't want to know!"

"Look, I'm not dumb. I'll be careful how I navigate through this process. I'm a married woman with three children and it was almost accidental that I ended up writing this book." But she has no regrets. "Writing it has given me such confidence. Knowledge really is power. All the people who've been involved with the book have said the same thing: once you know what you're doing, why you're doing it and how it feels for someone else, it makes a massive difference to what you're willing to do." Lucky Mr Godson, whoever he is.

? The Sex Book by Suzi Godson, Cassell Illustrated, £16.99.