RADIO / Tricks with time: Robert Hanks celebrates 21 years of an unchanging Kaleidoscope and a joyful Three Musketeers

Can it really be 20 years?' wondered Robert Dawson Scott last Monday, looking back at the first-ever Kaleidoscope. Given that he was hosting Kaleidoscope at 21 (Radio 4, Monday-Friday), you have to suspect that he hadn't been paying as much attention to the pre-publicity as he should have.

Point taken, though: the digest of that day's topics - a Rattigan double-bill, a biography of James Elroy Flecker and a picture-book on Constable - were more or less what you'd expect today, if delivered with more gravitas. The only item that stuck out was a bit about drugs to slow the heart down - for it's a long-buried truth that Kaleidoscope was originally a C P Snowy experiment in uniting science and art, although it wasn't long before they decided to abandon that approach. If you wanted, you could draw some depressing conclusions about what's wrong with this country.

On the whole, though, Kaleidoscope has done pretty well at maintaining its position as a genial, middlebrow critical forum which takes The Arts seriously without pretending that they actually matter (not, in the same way that taxes and earthquakes and getting the washing-machine mended matter). The position has weakened a little in the last couple of years, since the programme started going out live; it has tried to take advantage of this fact by being more topical, through daily arts news (which generally either tells you things you could find out about elsewhere or sounds as if it has been scraped from the bottom of the arts barrel) and through trying to relate the arts to current events.

Unfortunately, the odd Guernica aside, there is a bad tendency for topically inspired art to sound as though it has just come off the top of somebody's head. A case in point was last Thursday's appearance by a South African close-harmony group called Progress (former cast-members of Ipi Tombi, but they weren't keen to elaborate on that, and who can blame them?): their greeting for the new political dawn began 'Today will be the happiest day, / The happiest day of our lives / It feels so lovely to be free and gay, / Viva viva viva South Africa,' and carried on in this vein. This is the sort of lyrical imagination that gives benevolent despotism a good name.

Still, the failures of topical art just highlight the glories of the classics. In particular, a rather joyful serialisation of The Three Musketeers (Radio 4, Thursday) has just started. There are two main advantages to this version: the first a clever adaptation by James Saunders that messes around creatively with the time scheme, starting in the middle and hopping backwards at intervals to fill you in on the rationale.

The second is casting that defies easy rationalisation - specifically Timothy Spall as the dandyish Porthos ('You insult my shoulder-belt?'). He's very good, but you can't help suspecting that they must have given him the part for the incongruity of the thing. Martin Jenkins's production adopts a brisk pace and a jocose tone that seems just as well under the circumstances. This is what art was meant to be like.