Quick, hide - there's my ex!

What should you do when you bump into your ex unexpectedly? This is exactly what happened to Jude Law and Sadie Frost last week, at Dave Stewart's party in Covent Garden. When Jude heard that Sadie was on her way, he attempted to flee the bash - but, in an unfortunate piece of mistiming, bumped right into her on the way out.

It's a classic social dilemma, very rarely covered in the old etiquette books because nobody had exes in those days. So here are some useful guidelines for crossing this modern minefield with dignity.

Have loyal friends

Jude received a text message moments before Sadie's arrival, warning of the imminent disaster. Sadly, the warning backfired because Jude took too long to say his polite goodbyes, and looked somewhat ridiculous as he got caught creeping down the back stairs. But the principle is sound: have your spies posted around town, ready to tip you off. Just make sure to treat the bleep of your mobile like the wail of a fire alarm, and get out immediately.

Trade up

For maximum social confidence, each new partner needs to be better than the one before. The very last thing you want is that pitying glance which says, "You really couldn't improve on me, could you?" If you particularly despise your ex, try to be seen out with someone who excels in the areas where he failed.

If he was insecure about his height, date a giant. If he worried about his receding hairline, date a musician with a luxuriant ponytail. If he was a bit dim, date a professor. This should guarantee that any glimpse of you together will plunge him into bitterness and misery.

If you live near him, move away

The closer your home is to his, the more likely you are to bump into him in the back aisle of Budgens with your hair scraped back, your tracksuit covered in gym sweat and your basket full of treacle-puddings-for-one. Safest to see him only at parties where you've made an effort - or take the Joan Collins approach, and simply go everywhere in full make-up and evening dress. Presumably Joan does this because she's got so many exes, there's no avoiding them.

Maintain some mystique during the relationship

In those heady early days, it's tempting to share everything. The sex is great: why not tell him how much you'd enjoy it if he dressed in a fisherman's uniform? He's become your first loyalty: why not bitch about all your friends? You instinctively trust him: why not confess all your darkest secrets? Why not? Because you are lighting the long fuse of a powder keg which he will be clutching triumphantly when you see him after the break-up. It's terribly hard to be cool when you know that he knows that you know that he knows. So hold back at the start, and remember that some secrets should be kept until you're absolutely certain that you're with him 'til death.

Be friends with your exes

A nightmarish thought, perhaps, but much the simplest way. Manage this, and all the other tips become irrelevant. Exes can make wonderful friends anyway. When you first met, after all, you found each other delightful - bright, fun, attractive, endearing. This shouldn't all disappear just because you don't want to see each other naked any more. There is no danger in having lunch or seeing a film occasionally; personally, I'm capable of remaining fully clothed in the Odeon at least one visit in four.