Sometimes there's just no accounting for your own taste. Pheromones, hormones and/or desperation take over and you find yourself hugely attracted to someone who would never normally float your boat. He might be horribly ugly, horribly stupid or have horrible table manners – but whatever the problem, the fact is that as long as you're making love to him you just don't care. As long as no one else finds out, of course!

The pervert in you
And at first that won't matter. What's between you and your unlikely lover will almost certainly be purely physical, so seeing each other just in the bedroom should work out just fine for a time.

'All I wanted to do when I first met Andrew was have sex with him all the time,' says Christina from north London*. 'He was an academic and he looked like one – very geeky. The worst thing about him was that he wore this god-awful anorak - it was like something a very untrendy eight-year-old might wear. The best thing about him was that he was the best and most filthy lover I had ever met. He was very full-on with me. Kind of confident. And I just liked that, despite his nerdy looks.'

It's not unusual for women to find that being in a purely sexual secret relationship is incredibly liberating. We often let rip with a man who we know isn't going to be serious for us. Throwing caution to the wind, it's easier to own up to the sexual things we've always secretly fancied trying.

And this release of sleeping with someone who isn't going to figure hugely in your life is not only hugely erotic, it's also something you can learn from, sexually. Your inner sex goddess can rise up, actually telling you more clearly than ever before what you do and don't like sexually. Useful stuff - because when you do meet a man who you think could have staying power in your life, you'll know yourself better sexually.

In the meantime, having a secret sex life can be hard work. You mustn't get caught together – if you do, the magic of the relationship could dissipate. Plus there's the possibility that the longer you're with your geek, the more likely you are to fall in love with him. Oh yes, beware, it can happen!

The deep-thinker in you
Charlotte fell victim to this very phenomenon in 'Sex and the City' when she met Harry – he was bald, short, fat and generally not a looker, yet she was insanely attracted to him – and eventually her secret came out and Harry became her whole life.

The point here is that if you really fancy someone all that much, there could be something more long-term on the cards. Beauty really is only skin deep - disliking someone for their looks (or their anorak) is, er, shallow. Also, if the attraction doesn't wear off you may be forced to face crunch time. He may actually begin to ask to meet the other people in your life. Will you deny him that? Or will you find that he's wiggled his way into your heart as well as your underwear, and turn him from a secret lover into an official one? Gulp.

Andrea from Hertfordshire found that things had gone beyond sex for her. 'When I first met James he had this godawful moustache but I did fancy him, somehow – I wanted to get close to him.' The two of them made love in secret for months, and eventually it became impossible to hide him any more. 'I agreed to go out with James officially if he shaved off the moustache but he refused.' Andrea was aware that friends and family might think he looked odd but at the end of the day she wasn't prepared to lose him just because of that. 'Actually, I'd probably miss the moustache if it went now,' she now admits, although she still mocks him for it.

So the bottom line is, if you're seeing, or thinking of having a secret lover, get the most out of it – enjoy – but be ready to make the final decision: will he/won't he count? None of your friends will be there to discuss it with you, so it really will be a question that you – and you alone - will be able to answer…

*Names have been changed