Sarah Sands: Jude must learn the first Law of affairs

The appeal to Jude Law of playing Hamlet must have been the absence of vulgarity. In the darkness of the auditorium he would be treated as a theatre actor rather than a soap opera. And, indeed, his performance was textbook perfect – a little cautiously so. I noticed he had a graceful athleticism about him, but put that to the back of my mind.

Anyway, Law kept himself in check and was mildly reproached by some critics for the lack of sexual chemistry with Ophelia. So that makes a change.

The newspaper coverage Law envisaged must have been on the lines of: "Triumphant return to the stage." In his worst nightmares, he cannot have imagined the Sun's headline last week: "Jude knows he's been a Bard boy." Instead of Shakespeare forming a barrier between the actor and the popular press, the playwright has become the journalist's friend. "Alas, poor Jude, he is not well" began the Sun story about Law and the American model Samantha Burke, who has announced that she is carrying his child.

It seems to me that Law has made several miscalculations, apart from the obvious one. He thought that a run at the Donmar West End would diminish the public appetite. On the contrary, Donmar is the Vogue of the theatre world, it could not be more glamorous. If Jude had wanted to be obscure, he should have opted for the Savoy – or, these days, I'm afraid, the Almeida.

Rachel Weisz received more global attention last week for her performance in Donmar's Streetcar Named Desire than for her film roles. Acting ability raises your market value. Jordan would have to work her way through the entire British Olympic team to match the news interest around Helen Mirren's Phèdre.

There is another lesson for Law. I see no point in confining yourself to high art professionally if you then behave like a perplexed footballer in your private life. Law is not peculiarly promiscuous or accident prone. There are many other actors who are worse behaved. That is why they are actors, rather than civil servants. What makes him a Law unto himself is that he does not restrict his sexual relationships to his own circle.

It is the oldest rule of affairs that they are only safely conducted with those who have as much to lose as yourself. If Law had stuck to his leading ladies, none of this would have happened. No gun-at-the-head PR announcements about his delight at becoming a father, no fresh hell from celebrity websites.

His delight at finding the sweet shop always open is almost Clintonian. He is famous and he is handsome: is he surprised that he can always find women to hand? It is not a question of morality, but of discretion, the very thing he most craves.

Samantha Burke is a young model and actress from Florida who has attended an acting course to equip her for commercials and soap opera. She is already chatting away on her website about the pregnancy and has apparently named the child in advance. This is not Jackie Kennedy.

Law's troublesome nanny similarly felt that she had nothing to hide about their relationship. It is no use him refusing interviews and covering his head with a beanie hat when the women with whom he mixes are singing like skylarks.

The irritation for Jude Law, apart from the money and the complication, is that his Hamlet has been eclipsed by the hammer and tongs. He knows now that there's no protection in privacy: if only he had practised exclusivity.