Philip Hensher: Snobbery is just so tempting

"Pleased to meet you," Mrs Carole Middleton said on being presented to the Queen, and, if we are to believe the newspapers, went on to soil Her Majesty's ears by using the word "toilet". Add in the offence of simultaneously chewing gum - which seems, as a friend of mine observed, an implausibly showy hat-trick - and courtiers quickly came to the conclusion that Mrs Middleton, and by extension her daughter Kate, were unfit for polite society.

It might have been the gum-chewing, but the upper classes have always sought to distinguish themselves from the lower orders principally by means of their speech. Aspirational members of the middle classes, from the 1950s to the 1980s, purged their speech of its usages of "settee", "living room", "pardon", "home", "toilet", "serviette" and, in extreme cases, even "mirror". Inspired by Nancy Mitford's Noblesse Oblige, they practised saying "sofa", "sitting room", "what", "house", "loo", "napkin" and "looking-glass".

Upper-class usage has never been as unified or as static as glossaries suggest, however. It used to be vulgar to stress the first syllable in "balcony" or "peony", and few people now insist on "luncheon". Once all the middle classes had learnt not to say "pardon", the upper classes shifted their own usage; the Princess Royal, I believe, says "ee-ther", and I've heard the grand-daughter of a Duke say "toilet", and even "ever so". Perhaps it was meant as a joke.

In any case, the only firm rule seems to be that a word is common when somebody common says it - and what could be more common than a middle-class person pretentiously referring to a "looking-glass" in their "house"? When somebody posh uses a word, it becomes posh.

The dialect, or idiolect, of the aristocracy is, in short, designed to be impossible for anyone not born into it to master, and sometimes difficult for outsiders even to understand. When Princes William and Harry appeared on American television, their speech had to be subtitled.

The private speech of the ruling classes may be forbiddingly difficult for anyone trying to master it in real life. For a writer, however, it can hardly be anything but a seductive prospect. Everyone who has seen the Oscar-winning film The Queen, and heard Peter Morgan's screenplay, has commented on the extraordinary authenticity of its speech. The Queen, the Duke of Edinburgh, the Queen Mother, talk exactly as royalty of their generation must be supposed to talk. The Queen's characteristic crunching gear-change between direct, no-nonsense private speech and teeth-gritted formality when "on stage" is most exactly caught. Nothing in the Duke's outbursts or (a rather trickier case) the preserved pre-war socialite dialect of Queen Elizabeth strikes a false note.

However, the youngest royal character in the film with any speaking part is the Prince of Wales, at nearly 50. Morgan, wisely, limits his invented speech to characters in late-middle or old age. The speech of the upper classes of those generations, I think, has been thoroughly observed and catalogued; they speak very much as Mitford said they speak. To attempt a character younger than that - to try to do the deliberately baffling semi-Estuary posh of the young Waleses' circles - would be to invite disaster.

The private speech of the ruling classes has always been strewn with shibboleths, to determine who will and won't "do". A striking example of this has been chronicled in lavish detail in Armando Iannucci's brilliant New Labour sitcom, The Thick of It. In this version, the linguistic test is the ability to swear obscenely, inventively and plausibly. The female press officer does her best, but isn't very good at it, and gets excluded. The junior is overconfident, oversteps the mark with an obscene finger gesture, and gets excluded. The characters who can judge the correlation between their own status and their permitted degree of obscenity most exactly are the ones with the most power.

People with power will always try to guard and to extend that power. What Mrs Middleton has just discovered, and what Iannucci has elegantly demonstrated, is that the political elite ceaselessly attempt to extend their power even into notions of linguistic correctness. The elite, in The Thick of It, know, primarily, how to swear "correctly". The upper classes, we are to believe, know the "correct" way to refer to ordinary household objects, as if it were any more correct to say "lavatory" instead of "toilet", as if it were any less of a euphemism.

It's seductive material for a writer; it would be sensible, however, not to try to live your life by any of this invented correctness.

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