The Week In Radio: Still lapping up the delights of a shore-fire success

Making waves: 'Desert Island Discs' presenter Kirsty Young (BBC)

How has Desert Island Discs done it? How has it survived decades of culls and re-branding to become a broadcasting institution, seemingly impervious to change and yet still crushing the competition with ease? Of course, despite its shades of grandeur and infallibility, being an institution can be dangerous. They are liable to be remodelled or torn down altogether. You can just imagine some pipsqueak controller, desperate to ingratiate themselves with a younger audience, replacing presenter Kirsty Young with Fearne Cotton and rechristening it "Desert Island Downloads".

Happily, though, the programme created by Roy Plomley at home in his pyjamas has barely changed since its first recording in January 1942 in a bomb-damaged Maida Vale studio, although it wasn't until the late Fifties that castaways were given books and a luxury item to help pass the time on their island prison. Over the years there have been some startling moments: Diana Mosley's delight at Adolf Hitler's blue eyes; David Walliams's request for a gun in order that he might shoot himself. The records have often been eye-openers too, my favourite being George Clooney's request for William Shatner's version of "Lucy in the Sky with Diamonds" because "listening to it is so unpleasant it would force me to cut off my own leg, hollow it out and use it as a canoe to escape".

Indeed, much is made of the record choices, particularly those by politicians and their thinly-veiled attempts to appear hip. But music isn't the point of the programme. It is simply a device to trigger memories, music as a portal to the soul.

This week's castaway was the writer Vikram Seth, a sweet, self-deprecating man who was insufferable as a child, not least because of his habit, aged three, of challenging his parents' dinner guests to test his mathematical skills. As an adult, he spent 11 years studying for a PhD before impulsively abandoning it after reading Eugene Onegin. He decided to write a novel instead.

Despite his childhood precociousness, Seth developed into a more reserved adult and, until his thirties, struggled to look anyone in the eye. Now, aged 60, he admitted to periods of loneliness and longed for a partner with whom he could share his life. "I get seized with shyness," he confessed, "when it comes to expressing [myself] in matters of love. I wish I were more courageous in that regard. If I had to put my finger on a real shortcoming, it would be that."

Such an admission from a seemingly successful and self-reliant man underlines the humanity at the heart of Desert Island Discs. What is its secret? Perhaps the lapping waves in the theme tune lull guests into a sense of peacefulness and isolation that makes such confessions come easy. Or maybe it's down to Kirsty Young's skills as an interviewer, helped in no small part by her silkily authoritative voice that seeps out of the radio like molten steel.

Most crucial to its success, I think, is the fact that those who appear on it so clearly hold it in esteem and – perhaps with the exception of Morrissey who rumbled "next record" whenever things got uncomfortable – approach it in the spirit of openness. An invitation on to Desert Island Discs is a measure of one's ranking in the collective consciousness, up there with getting an OBE.

Next week the programme will be 70. In an age of endless restructuring, its longevity alone is worth celebrating. If I were marooned on a desert island I could pass a happy few months working my way through the programme's ever-growing online archive. It's what you might call buried treasure.