TRY this one for size: the only swimming-baths in your area announces that from six till nine every morning the Olympic-size pool only attracts enthusiastic, strong swimmers. In order to get in the non-swimming public, the pool will be closed down at those times and an inflatable paddling- pool provided instead. You'd think that was pretty stupid, wouldn't you? Well, that's a pretty fair analogy for what has just happened at Radio 3 - the warm, shallow splash of water in question being Petroc Trelawny, who has this week taken over as presenter the station's daily breakfast programme, On Air.

It would be nice to regale you with instances of Trelawny's idiocies but to be honest, none of them is terribly interesting or amusing; pure vacuity hardly ever is.

In any case, the issue is less how dull Trelawny is than why he takes so many opportunities to prove it. On Air has abandoned completely the practice of playing long spans of music in favour of snatches and fragments: one movement of Brahms's German Requiem, a quick aria from The Creation, a single song from the Auvergne, nothing more than five or six minutes long, and separated by Trelawny's flow of breezy chat. At the same time, the repertoire is being narrowed - Thursday was the fourth time in a fortnight I have heard one or more of the "Songs of the Auvergne" on Radio 3.

This isn't a matter of snobbery or musical elitism, it's a matter of having the pants irritated off you. That and good programming sense. Radio 3's unique selling-point was that it played pieces of classic music in their entirety; it created an opportunity for disengagement with the conversational hurly-burly of the world outside. Now it is simply an annoying clone of Classic FM. Trying to justify its existence by upping its ratings, it is wrecking the only genuine justification it has: that it provides something the commercial sector can't.

What's bizarre is that this musical self-disembowelling has been perpetrated in the same week that Tuesday evening's concert interval was turned over to wearily hallucinatory poems by the French Symbolists and the Postscript strand was devoted to the work of a single philosopher. (Though, disappointingly, David Cook's tribute to the influence of Alasdair MacIntyre's moral treatise, 'After Virtue', ended up a nostalgic commercial for a God-fearing society.) Radio 3 clearly doesn't think its listeners are stupid; it must just think they're not very interested in music.