Andrew Martin: When politicians get down with the kids, there's no way back up

Today, Nick Clegg appears on Desert Island Discs, and in the light of the week's events, this is important. The first question one wants to ask this co-architect of the coalition that has just inflicted the severest retrenchment since the 1920s is "Who do you think you are?"

Desert Island Discs – and we'll come to Clegg's choices in a minute – might be expected to throw some light on the case of this apparently bland individual. Ever since the programme began in 1942, certain selections by certain guest have provided stunning epiphanies. I can never think of Rowan Williams, Archbishop of Canterbury, without recalling that he chose "The Hedgehog's Song" by The Incredible String Band, at which point it occurred to me that Williams is, in fact, the continuation of the Incredible String Band by other means.

My affection for Spike Milligan was increased, which I would have thought hardly possible, when for his work of literature, he mordantly chose "the rent book".

Margaret Thatcher chose "Two Little Boys", which confirmed her mawkishness, and her deputy, the aristocratic William Whitelaw, went for the infantile "Run Rabbit Run", which might have charmed his friends but which, in the Old Labour Martin household, only confirmed his lack of brains. Whenever he appeared on television my dad would fume: "If that man had been born into an ordinary family he would be working today as a milkman." I apologise to any reader who is a milkman but it was always that profession that he lighted upon, which reminds me that David Cameron chose Benny Hill doing "Ernie (The Fastest Milkman in the West)", a very characteristic choice in that it was infuriatingly disarming.

Cameron is a better PR man than Clegg, whose choices are not endearing. They are too psephologically balanced, being a mix of the ethnic, classical, and white rock. We are asked to name no more than three in advance, and so I will pick out the three rock songs. They are "Life on Mars" by David Bowie, "The Cross" by Prince, and "Street Spirit" by Radiohead, an angst-ridden trio.

I believe Clegg made a mistake in not choosing eight classical pieces. In a dumbed-down world, we admire people who like complicated things. I remember hearing Derren Brown with Michael Berkeley on Private Passions, which is a sort of Oxbridge Desert Island Discs on Radio Three. I'd not much cared for Brown. He seemed over-confident on TV, and my children were too keen on him for my liking. But he chose the high point of Tudor choral music, "Spem in Alium" by Thomas Tallis.

In the course of that 40-voice motet, a lone, high voice provides an embellishment so exquisitely apt, so lonely, and so modern that it seems to transcend time. Afterwards, Brown left a reverent silence, before saying: "Such sweetness there, such sweetness." I've been a fan ever since.

I once read a short article giving advice on how to appear clever on Desert Island Discs. When asked "Is music important to you?" the reader was advised to say, "Not particularly, and I'm certainly no expert", thus going one up on the twit who says, "Yes, I'm a passionate music lover", and then chooses "My Way". The article prescribed a choice of eight classical pieces, which must include a late Beethoven piano sonata and Mozart's Clarinet Quintet.

That appeared back in the early Eighties when some people still thought that they ought to show an appreciation of classical music if they wanted to appear adult, never mind sophisticated. In Tom Stoppard's 1982 play The Real Thing, Henry, a high-brow playwright who has been invited on to Desert Island Discs wrestles with this: "I'm going to look a total prick aren't I, announcing that while I was telling the French existentialists where they got it wrong, I was spending the whole time listening to the Crystals singing "Da Doo Ron Ron"."

But you can't force it, and the last prime minister to opt for the classical full house was Ted Heath, and the number dwindled through his successors down to David Cameron who chose one classical piece, "On Wings of Song" by Mendelssohn, and that for the not very rarefied reason that "it was played at my wedding".

What most people do, including Clegg, is select a mixture of classical and pop, which I find unconvincing. I've always considered the genres so different that I can't see how they might co-exist in one mind. You end up with John Williams performing "Toccata" (actually Bach's Toccata and Fugue in D minor) on Top of the Pops in 1980 with his rock band sideline, Sky, sitting down in a turtle neck, with a drummer called Tristan.

In picking three rock songs, Clegg will know that he is being judged by the court of his peers: the generation aged between 35 and 70 for whom rock music is all important, the lingua franca. This is not true of the younger generation, for whom it is just one of many competing entertainments. I found a CD in my 14-year-old son's room the other day. I asked him to play it for me. It was wispy synth rock, and I said: "It's crap isn't it?" He shrugged and said: "Well, I'm listening to different stuff now." "But hang on a minute," I said. "Do you see what's wrong with it?" He didn't think it important either way.

The canon of great songs has been over-analysed, over-praised, sold off for adverts and ringtones. John Lennon is currently over-exposed for no better reason than that he would have been 70 had he lived. Keith Richards, perhaps the single most important role model for the post-war British male, has been blowing his cool all over The Times, talking up his autobiography, Life, which is published next week, and giving away all the secrets behind his songs.

Nick Hornby once ruefully admitted that the only subject about which he knew everything was the output of a fairly obscure soft rock band called The Bible, whereas once people knew all about The Bible. This resentment only increases our doctrinaire approach, our territoriality, which brings me to Clegg's three rock songs.

They're all "classics", roughly speaking, so perhaps he chose them to sell himself to Q readers, who are forever toying with the idea that The Bends, from which Clegg's choice, "Street Spirit", comes is "the best album ever".

But if we assume these songs bespeak something of his character, then we ought to probe further. The first question is whether we really want our politicians to be "into" rock music. Blair was. He said it was "the love of his life", and he is said to treasure a note from Keith Richards advising him to stick to his guns over Iraq: "Keep on rocking," it said.

But should a world statesman be "rocking" in the first place? Rock songs appeal to the turbulent emotions of the teenager. They preach sex, rebellion, iconoclasm, emotionalism. All three Clegg selections are of the portentous, adolescent starts-quiet-gets-louder sort, and they're all grim.

The lyrics of "The Cross" might have come from the pen of Adrian Mole himself: "Black day, stormy night/No love, no hope in sight." But there is the hope of redemption, or possibly just martyrdom "... if we can just... bear the cross".

I hope this song does not represent the Clegg credo. But for all his preppy demeanour, it may well be a window on the mind of a man whose party is at its lowest poll rating for 20 years, and who has just helped put the country's fate on a knife-edge.