Years ago some rather dissolute aristo- acquaintances of mine, who were friends in turn with some other dissolute aristos (they tend rather to run in packs) whose lands marched with the Prince of Wales’s Highgrove estate, told me this anecdote about the heir to the British throne: apparently Charles would often walk over to the house of these friends-of-friends, unaccompanied by his close-protection team, slip in their back door, plonk himself down at the kitchen table, and share a joint or three with his hosts, chatting jollily away and laughing uproariously the while. I don’t give this story a high degree of credence – if you’ll forgive the pun – although I devoutly wish to; after all, it both explains certain rather wayward tendencies in the prince’s behaviour, and helps to humanise someone, who by accident of birth is fated to forever exist first and foremost as a symbol, and only secondarily as a flesh-and-blood man. I don’t think Charles’s latest biographer would be fazed to learn her subject passes the dutchie on the left-hand side, although I suspect she’d worry, lest by doing so he ended up having to pass the Duchy of Cornwall on the left-hand side as well.

By which I mean to say: the future of the British monarchy concerns Catherine Mayer, although she’s an American by birth. Towards the end of this exhaustive yet entertaining biography she tackles the politics of the succession head on, arguing from the law of unintended consequences, and the pernickety nature of constitutional reform, to the conclusion that for all his inconsistencies and contradictions, Charles is, if not the best man for the job of head of state, certainly the most highly (sorry!) qualified. Mayer reaches this position by a slow and circular path, as if she were perambulating the landscaped garden of one of the many country properties the prince flits between on his own Dylanesque never-ending tour. Often she sits down under a gazebo to ponder weighty issues, and is joined there by one or other of her interviewees – among them the prince himself – but mostly she just surveys the terrain, attempting to divine the nature of the constant gardener from the topography itself. Mayer is too savvy to imagine she can fully render on the page a princely psyche that is not simply well defended by extreme and lifelong notoriety, but imprisoned within a metonymic cage; when she remarks – en passant – that the cavolo nero in a Highgrove flowerbed is pruned so as to resemble the three feathery plumes of the prince’s emblem, it isn’t because she believes God resides in that detail, it’s because that detail is all she has.

After all, what do we know about Prince Charles? Well, as a lifelong republican I like to think very little at all: I never consciously read anything about events on what Mayer terms “Planet Windsor”, I shy away from television screens when they sully them – I went to the Outer Hebrides a few years ago, in part to avoid the Queen’s golden jubilee. This being noted, the experience of reading this book was like telling a rosary: each little nugget of information, and every sincerely expressed opinion, was warmly familiar. As I reacquainted myself with the prince’s chilly childhood; his rigorous “character-forming” education at Gordonstoun; his search for “meaning” through bogus gurus such as Laurens van der Post and esoteric texts; his banjaxed “love life”; his charitable endeavours (really, he should be styled “Prince Chugger”) and his more politicised interventions in public life, it dawned on me that not only did I know a great deal about Prince Charles, but that on the whole – and certainly by contrast with the rest of his family – I rather liked him.

Facebook Twitter Pinterest Camilla, Duchess of Cornwall and Prince Charles share a joke as Raymond Blanc looks on during the 2014 Edible Garden Show. Photograph: WPA Pool/Getty Images

In particular I like him now, when, married into the upper reaches of bohemia, he’s at last beginning to resemble the old hippy he always has been, rather than the youthful straight-goer others believe he should be. Mayer’s book has sparked – or rather, reignited – some controversy: is Charles too “political” to be a constitutional monarch? Will he give up his obsessive beneficence when he seats himself on the Stone of Scone? And can he square his seemingly heterodox religious beliefs with his status as head of the Anglican Communion? But, again, Mayer is a shrewd enough surveyor of the British scene not to be fooled by such deceptively rational bends. She understands that the only real barriers to a smooth succession are emotional ones: the mass hysteria fomented by the cult of Diana Spencer and her mediatised martyrdom are still bubbling about in the British collective unconscious, and may yet erupt all over the primrose-yellow coat-dress of Queen Camilla.

In writing a biography of someone who is first and foremost a figuration, one that cannot by definition be transparent, the sensible course is to examine what exactly he’s a figuration of – and this is the approach Mayer adopts. Yes, she has some interview subjects: princely besties such as Emma Thompson and Nicholas Soames, but what they have to say is anodyne, while the positive remarks of staff members and campaigning associates is for the most part dreadfully dreary hagiography. On some of the hoo-ha the prince has triggered – from the “Spider” memos, to the seven boiled eggs, to his position on Islam – Mayer has had to rely on second and even third-hand testimony. However, this doesn’t matter, because by anatomising what the prince is emblematic of, she reacquaints us with – gulp! – ourselves.

I remember, aged eight, watching a blurry black-and-white prince being invested at Caernarfon Castle – I recall him singing the Goons’ “Ying Tong Song” on the radio, like an embarrassing and dweeby cousin. I think I must have witnessed the dreaded moment when he queried the semantics of the expression “in love” on national television, and I most certainly pored over the transcripts of the infamous Camillagate mobile-phone tap, in which the prince ardently yearned to become his lover’s sanitary protection. I used to think it was this latter outburst that, more than any of his other foibles, disqualified him from ruling – now, pace Mayer, I’m inclined to think it’s precisely this aspect of his character – at once passionate, surreal and whimsical – that renders him fit to be our king.

The key word here is “our”, for, when Mayer discusses the prince’s views on architecture, or his championing of the whacky philosophy of “perennialism”, or his forays into the deprived inner cities what I discern is that – whether consciously or not – he has modelled himself in our image. In common with his future subjects the prince is a bundle of poorly resolved contradictions. By instinct socially liberal but politically conservative, he – like all the rest of the Red Noses – tries to fill in the ever-widening gap between haves and have-nots with charity. Mayer begins by attending a fundraiser held by “The Boss” (which is how his court address him) for the “Bond Villains” (which is what he and they call their plutocratic quarry), and ends at one as well. This is surely just, because giving others’ dosh away is the best the prince can do, given he’s programmed to hang on to his own wholly arbitrary privileges for grim death. The building of Poundbury, the prince’s bizarre Dorset Petit Trianon, and his attack on architectural modernism in general, is motivated not simply by a knee-jerk reaction, but by an underlying philosophy of sacred geometry founded in “biomimetics”; the notion that humans divorce themselves from the structures of the natural world at their peril. These views, set out in his own 2010 book Harmony, are in large part twaddle, of course, but well-meaning twaddle; and, as Mayer is at pains to point out, the prince’s belief system is no more rackety and confused than most people’s. What’s more, in reading her account of his interventions into the politics of the built environment, beginning with his infamous 1983 “monstrous carbuncle” speech, it occurred to me that while his answers might be painfully banal, he undoubtedly asks the right questions.

Employing a sort of “low baroque” prose, featuring such nail-snagging tropes as “cantillating with gusto” and “under pressure to cut some existing liegemen adrift”, Mayer exhaustively shades in her pen portrait of Britain over the past half-century, and in so doing the prince’s own baffled visage emerges: the eternally disappointing son of flintily determined parents, he seeks everywhere to emotionally connect, yet is doomed to forever be cut off by the glassy cage of his metonymy, one formed by the myriad lenses he continues to compulsively mug it up for. Several times Mayer observes that Charles and Diana had more in common with each other than they ever realised; he may seem a highly intelligent and thoughtful man, but I fear this is only by contrast with his notably stolid stablemates. If he were the truly subversive figure implied by my own dope-smoking anecdote, then like his late first wife – although for very different reasons – he might have smashed this cage to smithereens.

In that case I think we could, possibly, have moved forward to a republic with some degree of consensus, but since Chucky is determined to be our king, and since – as I hope I’ve demonstrated – there’s a high degree of congruence between us and him, there’s probably nothing we can do but sit back and enjoy the carriage drive. Who knows, judging by his recent forays in the Middle East, and his comments on Islamist radicalisation in Britain, Charles isn’t going to let up, but will go on flying a flag that embodies so many paradoxes it might well have been designed by MC Escher … while stoned out of his brain.

• The paperback of Will Self’s latest novel, Shark, will be published by Penguin in March. To order Charles: The Heart of a King for £16 go to bookshop.theguardian.com or call 0330 333 6846.