Mini-misanthrope ... Nigel Molesworth

If you'll bear with me a moment, I'm going to make an unlikely connection between the gravitational pull of Jupiter and the new St Trinian's film. Without Jupiter, Earth might long since have been rendered uninhabitable by collisions with the many asteroids and comets which hurtle around this neck of the cosmos, quite heedless of our fragile biosystem. But thanks to Jupiter's giant mass, most of these extraterrestrial menaces have been handily diverted out of harm's way.

So it is with St Trinian's, and anything else created by that authentic genius of British graphic humour, Ronald Searle. So powerful is the allure of putting a selection of the dolly birds du jour into school uniform that it draws potentially unwelcome attention away from Searle's more brilliant work.

It's inevitable that the naughty (although only latterly highly sexualised) schoolgirls should be Searle's best-remembered and most frequently revived creations; but his greatest invention was another, far less enticing playground figure, Nigel Molesworth. Molesworth is the splendidly jaded and misanthropic boy, a reluctant pupil at St Custards prep, who features in a series of books written by Geoffrey Willans and illustrated by Searle, and whose very grubbiness has left him mercifully untouched by the likes of those who would condemn the Belles of St Trinian's to modern incarnations.

Before a low-wattage bulb lights up above the head of any producer who might happen upon this, let me add that Molesworth is inherently unfilmable. Any attempt to put him on the screen would surely result in not only artistic but commercial calamity. Firstly, it is Willans's expert conjuring of the character's voice, combined with Searle's uniquely expressive illustrations, that make Molesworth live. He is purely a creature of the printed page, and his surly, beetle-browed shrewdness and ingeniously illiterate turns of phrase will not survive away from it.

And secondly, just as St Trinian's was devised to mock the jolly-hockey-sticks genre of girls'-school fiction, so Molesworth was a (much more sophisticated) satire upon not only 1950s Britain, but also minor public schools, and the Billy Bunterish stories associated with them - a style which has enjoyed a staggering revival in the hackneyed environs of Hogwarts (the name may have been lifted from a Molesworth chapter). St Custards is the antithesis of Hogwarts, and of every cosy cliché it represents. It would by its nature repel the millions drawn to Harry Potter's alma mater.

Molesworth has hardly dated, because the glum, provincial Britain he inhabits, with its petty snobberies and doomed aspirations, still exists; and because the anarchy, imagination and mordant humour with which he confronts it feel as fresh as ever. The Molesworth tetralogy belongs alongside such darkly comic classics as Lucky Jim and The Girls of Slender Means, all of them being entirely of their time and place - post-war Britain - yet dealing drolly with universal themes. If anyone does get it into his head to film it, I hope he gets hit by an asteroid first.