Prince Charles achieved the near impossible recently by making a stand-up comedian laugh - at himself, no less.

More used to being the butt of ridicule than the author of a joke, the first in line to the throne found himself in the company of comic Des Clarke at the Prince's Trust Awards in London last week. Clarke introduced himself by saying he was from Glasgow. Charles said he'd already spotted that by the way he spoke. Impressed, Clarke then asked if his royal highness was at ease with the Scottish accent. "Oh yes, fantastic," replied Charles, "until you've had a couple of drinks. I'll make sure that I don't speak to you after five o'clock."

In fact, alcohol is not required for some Scottish accents to be trickier to understand than quantum physics. I have one colleague whose conversation feels like being in a total-immersion foreign language course, where you daren't ask someone to repeat themselves, but wish you could replay every utterance at half-speed.

The west of Scotland, however, is a bastion of clarity compared to the obscurities of the Doric, into which linguistic arena I was thrown as a child. This was Scots as I'd never heard it before. I could tell it was beautiful, like the sound of pibroch or a Gaelic lament, but whether they were asking if I wanted another buttery, or needed a lift into town, I hadn't a clue.

There is a certain irony, though, in someone of Prince Charles's class admitting defeat in the face of a Caledonian accent. I say this not because he spends part of each year at the family's country pile at Balmoral. The Scots spoken in that region could probably qualify as the most pure and unsullied in the British Isles. What amuses me is the aristocratic drawl itself. Whereas the working and middle classes of Britain speak with accents ranging from opaque as woolly tights to the clarity of Edinburgh crystal, toffs speak as one. A Hebridean lord will talk just like his Kentish counterpart, a language that sounds as if the tonsils and soft palate have undergone drastic surgery. When Charles was roundly mocked for admitting he talked to his plants, I'm surprised nobody thought to ask, would they have understood him?

Gone, thankfully, are the days of the worst excrescences of Received Pronunciation, which kept the BBC in such a stranglehold one suspects a gun was held to presenters' heads lest they shorten a vowel when it could be stretched to infinity. Even so, when we were at St Andrews University, my friends and I discovered to our chagrin that we were obviously speaking a version of English more suited to Tam O'Shanter or Piers Ploughman, while those from the upper social echelons could have walked straight on to the set of Brideshead Revisited - or, indeed, into a Cabinet post. By the end of four years, "yah" had crept unnoticed into our vocabulary in place of yes, though the return to real life quickly stamped that affectation out of most of us.

Perhaps the dull uniformity of the posh accent explains why very few novelists attempt to reproduce the etiolated articulation of the aristocracy - that, and fear of using too much paper. Meanwhile, regional dialects are a staple of fiction and drama, often for comic relief, sometimes for sinister effect but, thankfully, now usually for realistic effect. Yet when I was young, reading Evelyn Waugh or Anthony Powell, whose characters hailed from the better public schools, we assumed that they were speaking perfect English while those of us from beyond the privileged pale were oikishly crude. Had these literary figures stepped off the page, though, it would have sounded like the string section of an orchestra tuning up - a caterwauling of strange, dissonant, unnatural wails, harder by far to fathom than any loon from Aberdeen.

It has always astonished me that, despite the evidence of our own ears, it was for centuries an axiom that the upper classes were the true custodians of English as it should be spoken. Prince Charles may have trouble with comprehending Scots after they've knocked back a pint or several, but imagine visiting Highgrove after pre-prandial drinks. People would be talking as if they had billiard balls let alone marbles in their mouths. Not just ordinary marbles, either, but the sort Lord Elgin lugged back from Greece.