Pygmalion is returning to the London stage in a production for the Old Vic by Peter O'Toole. I can't wait. The play is, as George Bernard Shaw triumphantly observed, “so intensely didactic... that I delight in throwing it at the heads of the wiseacres who repeat the parrot cry that art should never be didactic. It goes to prove my contention that art should never be anything else.”

Shaw's Pygmalion is, however, a melancholy reminder that phonetically, England is not the place it once was. The first Act has a brilliant scene in which Henry Higgins is surrounded by an angry crowd and identifies in turn exactly where the people who address him come from. Eliza, he says decisively, comes from Lisson Grove, a bystander from Hoxton. But it is not only the lower orders he can place phonetically as exactly as a botanist might some exotic bloom - Freddy Eynsford Hill's sister is Earl's Court; his mother from Epsom; Colonel Pickering is Cheltenham, Harrow, Cambridge and India.

Is there any place where such a feat would still be possible? Certainly not London, where the accents of Hoxton, Earl's Court and Lisson Grove are indistinguishable, at least in terms of the white English. It's partly because few people in the capital actually live where their parents grew up, partly because London is now divided phonetically on generational, not local, grounds. Freddy's great-granddaughters almost certainly have the Australian uplift at the end of their sentences - you know?

His great-grandsons will sound a bit like Prince Harry, with a deliberately downbeat take on the vernacular. In fact, a really successful contemporary Sloane will sound a bit Rasta. It's a kind of survival mechanism - the phonetic equivalent of dressing from Gap - and with luck will stop you getting beaten up when you open your mouth in mixed company. The one place where, until recently, Professor Higgins's skills survived was Northern Ireland during the Troubles. There you could identify not just someone's religion but the part of town they came from as soon as they opened their mouth: you had to.

The other aspect of changing diction is something that Shaw would have disliked intensely - a diminution in articulacy. The one person I know who maintains the standard of elocution of the generation before last is the art critic Brian Sewell. But he insists he does not have an accent at all.

Of course, the old bores in linguistics departments will maintain that English is a vibrant, ever-changing language. So it is. But the fact that the multifarious accents of Shaw's time - including his own Protestant Irish diction - have disappeared as utterly as Nineveh and Tyre is a change for the worse.

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