The most fascinating stars know that a life in motion is far more interesting than one that appears stagnant. It doesn’t really matter whether their trajectory is upwards to career success and inspiring charity work, or downwards to addiction and tragedy. As long as they keep their lives moving, we keep watching.

Madonna set the pace in the late 1980s, with her constantly changing image, but these days, wearing a new wig every few months is not enough. Lindsay Lohan changes her outfit three times daily, and her boyfriends with similar frequency. Clever stars know that they must always be seen to be doing things. Whether launching a new hairstyle (Posh), fighting an eating disorder (Mary-Kate Olsen), surviving a divorce (Jennifer Aniston) or battling cancer (Kylie), modern celebrities have to constantly be at the centre of a narrative. And the more it looks like a trashy soap opera, the better.

Take Jade Goody, who has spared us no detail of her train-wreck existence. From getting drunk to having breast implants to crashing her Porsche, Jade is always giving us something to talk about.

The same can be said of Jordan, who offers us not one but two folk to gossip about — herself and her alter ego, Katie Price. Simultaneously, we can tut over Jordan’s slutty outfits and marvel at how Katie copes with little handicapped Harvey. Genius.

Angelina Jolie manages her fame trajectory with consummate skill. Just when the world was ready to hate her for splitting up Jen and Brad, she adopted an African orphan and became a campaigner against Aids and poverty. Then she had a baby with the most beautiful man on earth, but instead of giving her public the satisfaction of a happy ending, she has so far refused to marry him. Rumours of tension in the Brangelina relationship serve only to keep us interested.

Perhaps Angelina knows that happy endings are often career death. Nicole Kidman, for instance, is much less enthralling now that she’s comfortably settled with her new husband, Keith Urban. We loved watching her survive divorce and look for new love, but now her trajectory is flatlining, and unless she does something soon — puts on masses of weight, say, or has a baby, or wins another Oscar — her star will wane.

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