When a format has been alive longer than you have, its place in your life is more like that of a family member than a programme. Desert Island Discs wound itself round my heart like a parent in a Seamus Heaney poem, an inimitable combination of constancy and range, the steady soporific tempo of its theme tune bookending a conversation that never hit the same spots twice, or at least, never in the same order.
Somewhere around the turn of the century, Sue Lawley began to irritate the hell out of me, for reasons that were hard to articulate because they were mainly very unfair. I used to hate the way she’d start the university segment, “and then … Oxford”, elongating, even caressing the word as if it were made of purest, gold-plated caviar. I got it into my head that when Carl Djerassi, inventor of the pill, chose Mahler’s Kindertotenlieder as his favourite track, she said “Really? The Mahler?”, doing a solid impression of a person who’d forgotten Djerassi’s daughter had killed herself. (I just went back and listened to it again, and this is completely wrong: she just says “Mahler” matter-of-factly.) The truly memorable thing about that interview was that she unearthed, in the rigorous research process, the fact that Djerassi had a cross-trainer at home which he used naked; Lawley, disapproving by default, had something that she could legitimately disapprove of and she sounded tickled pink.

Then, of course, Kirsty Young took over, and it wasn’t the same. It was as wildly different as two people doing the same job could be, and I missed Lawley as sorely as an aunt, with total amnesia for all the rude and baseless things I’d said about her. But Young owned the island: she owns it still. When she leaves, most likely to start a social enterprise that links war-ravaged teenagers to tech giants, the consolation that the format is larger than the presenter will be very thin. She has the rare and simple gift of sounding warmly interested in people’s lives, which is the best way to approach almost everybody, except David Cameron.
The programme rarely makes news – it isn’t Vanity Fair, it doesn’t explode any landmines. Things are incredible in retrospect – Diana Mosley’s Holocaust denial was quite a marmalade-dropper – but the show offers a valuable snapshot of an era. This is partly because it prides itself, still, on an anti or, rather, pre-celebrity approach to human achievement, where David Nott, a doctor who has performed reconstructive surgery in the Gaza Strip, is as noteworthy as Davina McCall (you can imagine a world in which someone would say Nott is much more noteworthy than McCall, but that world is not this desert island). Partly it’s because it’s often looking back on a person’s life, by which time most things they want to spring upon the world have already been sprung. But one gets the sense that if someone did try to drop a bombshell – say Edwina Currie hadn’t already told everyone about her four-year affair with John Major and tried to tell Young – they would be delicately informed that it wasn’t required.
Since so much of what we consider a revealing interview is in the things we didn’t already know, this makes it hard to define exactly why Desert Island Discs feels so intimate. The research is sterling, it leaps off each conversation. So that helps. But naturally – and this is where all plaudits really belong to Roy Plomley (no, I didn’t know it was spelt like that either) – the music cracks open even the most reserved character. The act of sharing one’s favourite songs is, in itself, so personal, so truthful, that to try to then introduce any reserve, let alone any caginess or defensiveness, would be both difficult and obscurely unnecessary. You are, by definition, showing your human face, even if you’re pretending to like Bartók more than you actually do; you could re-fix your mask to talk about your early life, but really, why would you?

The one exception to this – except David Cameron – is some actors, who sound like a person playing a person who has been invited on Desert Island Discs. It is a dangerous game, imperilling your soul to pretend to be someone else, as George Bernard Shaw once sort-of said.
With that intimacy, the programme brings – not always, but memorably – rumination on death. It is impossible to talk honestly about one’s life, leastways over the age of 40, without talking about those you’ve lost. Emma Thompson had some brilliantly personal choices, including her friend Patrick Doyle, who wrote a song about her house, but the one that created its own neural pathway in the nation’s brain is her father, Eric, narrating The Magic Roundabout. Her memories of him, while moving in their careful particularity, were universal in the kernel – that her favourite thing was to make him laugh. It was a moment, of thousands, that made you feel closer to your species.
Naturally, there is a sharp piquancy to an interview with a person who is now dead, painful but nourishing, like calling someone’s voicemail to hear their voice. I strongly discourage, if you’re wearing mascara, going back to listen to Victoria Wood’s choices.
Everybody normal has their own Desert Island Discs shortlist, periodically refreshed as a new phase starts or ends, ready like the packed bag of a man on the run. Mine sometimes has an accidental Radio 4 theme – for ages, I would have had Rob Brydon singing “Danny Boy” on I’m Sorry I Haven’t a Clue. He got knocked off by Jesse’s tear-jerking rejection song in Toy Story 2, but that was my baby-years list – tired and emotional, watching too many cartoons – and it needs a refresh.
The curious thing is that the openness from the interviewees is rewarded by a kind of dignified interest from the listener, an instinctive rejection of prying or prurience; I remember far more about people’s musical choices than I do about their personal lives. I couldn’t tell you thing one about Ralph Fiennes’s family, but I can scarcely look at him, 17 years later, without hearing Nina Simone singing “Feeling Good”. There is nothing like the disappointment of a subject who just doesn’t like music that much, and stuffs their choices with “amusing” Victorian music hall hits and spoken word. Yet it is, frankly, incredible how rare that is – unless there is a cutting-room floor somewhere, full of tone-deaf Nobel prize-winners. Music as an expression, not just of oneself but of one’s best self, seems to be a thread running through us all, weaving us into a meaningful tapestry.
Except David Cameron.
• There is a comprehensive Desert Island Discs archive at bbc.co.uk.