Desert Island Discs (R4), like Today or The Archers, is a British institution. An extract from one of these three is immediately recognisable and can often form the major topic of newspaper leaders. Recently, Lawley was perceived to have questioned Gordon Brown MP too closely about why he was unmarried. If you actually listened, you would have heard very little to fuss about, and Brown himself seemed quite unbothered by her probing - but you didn't have to listen. One foot out of line and Lawley's whole existence becomes the subject of national debate.
Yet she is a worthy successor to the programme's ``onlie begetter'', the late lamented Roy Plomley. He was inclined to tell the story of his grand idea at every possible opportunity. In November 1941, he would say, he was cold in his pyjamas one night when his brainwave occurred, out of the blue. This was a little disingenuous. Two earlier magazines - The Music Teacher and Rhythm - had already tried asking their readers to suggest what music they would enjoy if marooned on a desert island, and it is likely that Plomley had seen them.
Be that as it may, the programme was Plomley's for life. It began by being at least two-thirds music, with only seven minutes of conversation scheduled. (Those listeners who miss that particular arrangement are discovering that it still exists on Saturday mornings, under the benign and definitely un-probing management of Michael Berkeley in Private Passions on R3.) These days, the music matters less: castaways are required to talk for about 27 of the 40 minutes. Gradually, too, the idea of more baggage has evolved, in the form of a book and a luxury to accompany the castaway (originally called the "shipwreckee"), and the whole concept has changed. It has become an opportunity to discover the real character of famous people, revealed, of course, by their choices, and by their answers to standard, if whimsical questions.
Some manage better than others. Nobody who heard it will ever forget Otto Preminger's ferocious response to Plomley's routine question about building a shelter. "A hut?" he thundered. "Vy should I be vanting a hut? And vy are you going red in ze face - and vair your hair should be?" Sue Lawley tends to rephrase the question - once, marvellously, asking Frank Bruno if he was good with his hands - but at least she plays the shipwreck game. Michael Parkinson, the first, disastrous Plomley replacement, could never enter the spirit of the thing.
Lawley combines the fantasy element with a convincing interest in each of her subjects. Inevitably, she does better with some than others. Recent successes have included the delightful old silent-movie star Chili Bouchier, a real find, who cheerfully admitted to disgraceful behaviour in the Harrods Small Ladies department, and Pauline Quirke, who completely demolished the vision of her presented by her television roles and proved to be utterly charming.
Only occasionally does Lawley give up and sound bored. A recent example was her interview with the impresario Michael White - nothing to do with my esteemed colleague of the same name. This was a 60-year-old obsessed with staying young, whose voice and choice of music were so tiresome as to make you want to serve lunch early. In the event, I stayed long enough to discover, to my satisfaction, that, of course, his book was to be Proust and that his luxury was a blooming bicycle. Last week's guest looked to be equally unpromising: the integrity of a successful businessman seldom survives the flattery that surrounds him. Yet Lawley brought out the best in Gerry Robinson, who responded gamely and, apparently, accurately, as she asked him exactly how much money he had made. It was, by that point, what we all wanted to know.
Self-delusion does not last long on the island. We addicts soon spot the castaways who, like the character in Tom Stoppard's play The Real Thing, are determined to choose far more highbrow pleasures than they can sustain in conversation. Some deliberately set themselves up: Mai Zetterling insisted on an extra record made up solely of applause, which she couldn't survive without. And politicians have a doomed tendency to choose tub- thumping music to emphasise their patriotism, which nobody could survive for long with.
Though the Prince of Wales was probably right to decline the invitation, few others can resist. It has become the supreme accolade of success, far better than a knighthood. When Susan Hill ended her interview, some time ago, she sighed that now she had no ambitions left, nothing more to dream of. In fact a few years later, they asked her again, as sometimes happens to the best of them.
In the end, it is often the luxuries you remember. Invited back for the third time, Dame Eva Turner, by then as old as Methuselah, chose castanets so that she could return and play Carmen; Terry Jones chose dry sherry, because he needed a glassful before Sunday lunch; Hermione Gingold felt that she required the Albert Memorial and Alfred Hitchcock had a railway timetable. Three people, including Stephen Fry, have wanted instruments of suicide. Can't wait to hear what Peggy Mount will choose, at about 12.50. It's a good game to play, just in case they ever ask you. What would you have? I can't think why nobody ever asks for Room Service.