Editor-At-Large: Believe me, Madonna, I've been there . . .

The big question on everyone's lips at the moment is "why did she do it?". Madonna's West End stage debut last Thursday evening marked one of her weirdest career decisions yet. The curtain rose on a solitary figure, centre stage. Cue tumultuous applause and cheers.

Not for her the everyday challenge of learning a new language or painting watercolours. Mind you, what thrills are left? Madonna's honed her body to perfection; how many 40-year- olds can match those rock-hard upper arms?

She's got a very attractive, nice husband and two children. Put her on a concert stage and she trounces Kylie any day. So why did Madonna sign up for a second-rate play that would involve her learning thousands of lines, complicated manoeuvres, a couple of tacky sex scenes and a supporting cast who would (without having to try too hard) upstage her just by their ability to project beyond row J of the stalls?

Madonna is ludicrously exposed as the central character, a scheming art dealer. She has to utter the lines that start and end the evening. She has to wave a large floppy black dildo about and pretend to enthuse about sex with a scraggy millionairess. At the end, I breathed a sigh of relief that she got through without disgracing herself. In fact, given her limitations, Madonna did amazingly well. The question remains, though, why? I think I can shed light on the puzzle.

Twenty-five years ago, I was presenting two television series a week, earning pots of money and as busy as all hell. The playwright Heathcote Williams called and asked if I would be interested in performing in one of his pieces, The Immortalist, at the ICA, in a lunchtime theatre season. Any sane person can spot that I am unable to play anyone except Janet Street-Porter, and performing is something best confined to a close circle of trusted friends after a lot of drinks. I am the woman who failed miserably on Give Us a Clue, being roundly beaten by Bernie Winters. (The shame.) Nevertheless, my ego took over, and for two weeks I paced the stage at the ICA trying to look like a television interviewer, furtively reading my lines off a clipboard. I was rubbish, but we are talking fringe event attended by a select few. Emboldened by this experience, I was thrilled when award-winning director Philip Saville cast me in a BBC2 drama by David Halliwell playing opposite Donald Pleasance.

By then I regularly interviewed stars on television, but memorising chunks of conversation and spouting them while moving around defeated me. Donald suggested that I tape my part and play it back while I ironed. The sound of my own strangulated voice removed any remaining confidence. I stopped ironing and did relaxation exercises while holding hands with the cast. The play, Meriel, was broadcast in 1978. Luckily it vanished, trounced in the ratings by an ITV documentary made by a man I subsequently married, grateful to him for obliterating my major career mistake.

So on Thursday my heart went out to Madge. This is what happens when those around you are too scared of your steely temperament to tell you the big No word. I've had dinner with Madonna a couple of times – she's smart, ruthless and focused. But not someone you'd want to remind of their limitations. Her relentless quest to extend herself is admirable, and touching.

Meanwhile, can any critique of my acting career be limited to my debut in Antonioni's Blow-Up, where I dance silently in a pair of silver plastic trousers hoping my fake eyelashes won't fall off, or my brief scene in a 1960s Italian film by Tinto Brass, in which I play a hairdresser's receptionist (silent) who leads Claudia Cardinale to a washbasin where a woman is wearing a papier-mâché horse head?

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Much has been written about the compulsive qualities of 24, starring Kiefer Sutherland, on BBC2 and BBC Choice every Sunday evening. I've succumbed, finding it easy to kiss goodbye to The Forsyte Saga and Gina McKee with her limited range of facial expressions – cod, halibut or brill.

24 is an elaborate conceit, purporting to follow the events of one day in real time during an assassination attempt on a black election candidate. Sutherland plays Jack Bauer, the boss of a counter-terrorism unit, whose wife and daughter have been kidnapped. The twists and turns of the plot are engrossing and unpredictable, which is a polite way of saying risible. Nevertheless, it is excellently shot and designed, using split screens to move the various strands of plot along. Some critics have lamented the fact that it couldn't be made here. Well, I disagree.

24 has been on BBC1 for years. It's a huge success. It's compulsive; it interweaves five stories at once. Once tuned in, you cannot switch it off. Our version is called Casualty. OK, Charlie is still wearing that glum, slightly perplexed expression he had 10 years ago, but don't let that blind you to the sheer brilliance of this as a piece of contemporary drama.

Like 24, Casualty takes place in one night. A lot of the action is in real time. Without resorting to split screens, a mass audience follows at least three unfolding stories at once. Every social issue has been addressed in the past year. 24 is great fun, but we still make some of the best television in the world on far lower budgets than our American rivals.

jsp@independent.co.uk