What hope for a boy born to be king?

It is a social reflex that those discussing the behaviour of the Prince and Princess of Wales mutter at some point: 'the poor children'. But this sentimental afterthought should really be a hard-headed forethought. For Prince William Arthur Philip Louis is probably the most interesting figure in the current constitutional quasi-crisis. Although he has not yet published a book - perhaps he is even now working with a Blue Peter presenter on the authorised child's-eye account - it is in the person of Prince William, aged 12, that the true scale of the crisis surrounding the British monarchy becomes clear.

Prince William - or 'Wills' as they like to refer to him - is the consolation of frightened monarchists. Their intellectual position might be summarised by the phrase: 'Where there's a Wills, there's a way.' The Sunday Express, now edited by the thundering patriot Brian Hitchen, exists to reassure older Britons that all is well in the realm. So it was not surprising that the newspaper's angle on the present regal hysterias should have been a report that the Queen Mother was manoeuvring to install Prince William as heir to the throne in place of his father.

Nervous Palace-backing Conservative MPs are to be heard telling journalists that the answer to the Windsors' difficulties is to 'skip a generation'.

Even those Royalists who believe that Charles should remain heir, assume - given the history among the Windsors of extreme female longevity and male frailty - that his reign would be a short one. They too are, in effect, banking on Wills.

Monarchists feel better when they mention William. He is their spare parachute, the rip-cord they reach for when they feel themselves falling.

Yet this security seems to me a terrible illusion. It is in the Wills Scenario that we see the serious weaknesses - intellectual and practical - in the position of those trying to shore up the House of Windsor.

The traditional complaint against using the substitutes' bench - that generational continuity is the whole point, that monarchy depends on pot luck - is knocked out by recent British history. The Prince of Wales's own grandfather was a tangent to the succession. The difficulty is not the skipping but the unthinking optimism about the monarch they are skipping to.

The first objection to the generation game now being played is the unformed personality of someone not yet even a teenager. Monarchists find William more palatable than his father. But which of the characteristics that they find objectionable in the Prince of Wales - adultery, emotional coldness, mysticism - would have been apparent when Charles was 12? Relying on the reign of King William is a bit like a general election campaign conducted solely with pictures of the candidates as babies. It is worth remembering that those who taunt advocates of republicanism with the line, 'OK, who would you have as president?' are themselves venerating a 12-year-old kid.

No sane mother or father would make such implacable assumptions about their own young child. In the next few years, Prince William could be revealed as a homosexual or a republican: either of which might pose a problem for those monarchists now building up his cult. Nor does having a title and growing up in a big house preclude difficulties with drink or drugs, as the case of the Marquess of Blandford sharply reminds us.

Given that we are also looking at a future Head of the Church of England, spiritual allegiance may well prove a particular difficulty. This child has grown up between a mother reportedly toying with Roman Catholicism and seances and a father directed by his guru Sir Laurens van der Post towards Eastern mysticism; not to mention his aunt Fergie very probably hymning the virtues of colonic irrigation on her visits. Staring wide-eyed at this cafeteria of philosophical options, do we necessarily back the young boy to pick Anglicanism? At the moment, the Archbishop of Canterbury only has to worry about whether he can crown a divorced man. With William, the Synod may find itself debating the suitability of a Buddhist or a Moonie.

It is in the matter of the influences to which these impressionable boys have been exposed by their parents that the campaign for King Will encounters its biggest problem. Consider the nature of the conventional case against Charles. He is thought unfit to rule because of his behaviour (adultery, emotional cruelty), but also because of his general character.

Post-Dimbleby, we attribute these problems to the nature of his upbringing.

Yet if we accept the assumption that childhood wounds, what are the prospects for Prince William?

Charles's cruel youth amounts - as Dimbleby presents it - to a dour public school, a father who was a bit of a bastard, and a mother who was away a lot reigning. William's, however, encompasses the most public marriage breakdown in the history of the world, a mother who tried to commit suicide, and a father who, in his obvious unhappiness, may not have been the perfect advertisement for the job of heir to the throne. The best hope for Royalists is probably that the Wales family follows the pattern of the one in the sitcom Absolutely Fabulous, where the child has rebelled against her parents by being serious and mature.

Loyal subjects of the Crown may choose to ignore these possibilities - to assume that Prince William will emerge undamaged from the palace of horrors.

Yet even if he were to, and the British throne were to survive until he was ready to ascend to it, has it never occurred to the adherents of this 12-year-old that he may not, when older, want the job? There is a passage in Andrew Morton's Diana: Her True Story, now recognised as authoritative, which aims to be heart-warming but is actually chilling: 'William and Harry . . . are now aware of their destiny. On one occasion, the boys were discussing their futures with Diana. 'When I grow up I want to be a policeman and look after you mummy,' said William lovingly. Quick as a flash Harry replied, with a note of triumph in his voice, 'Oh no, you can't, you've got to be king.' '

Morton presents this as an anecdote about the kid who would be king being 'aware of his destiny', but, in fact, if read closely, it's a story about a little boy who wants to be a policeman when he grows up, and is already aware of the suffering in his parents' marriage. And I would guess that the reason little Harry sounded 'triumphant' was that the sense of his comment was: 'You've got to be king.'

That was two years ago, and the time since then has provided the boys with an even worse commercial for the Royal life. Liking to refer to themselves as 'The Firm', the Windsors should be aware that many family firms have collapsed because the sons simply did not want to be accountants, or builders, or farmers, or, in this case, kings. Realising in his teenage years that he is surrounded by emotional head-cases of various kinds - followed, as his sex and drinking life begins, by a press more intrusive than anything his father suffered - Prince William might understandably decide to go back-packing in Nepal and not come back.