"Nowadays, it seems like experts give birth to a new theory every few minutes," said Andy Hamilton at the beginning of It's Only a Theory. I don't know about that, but if so they're at least matched by comedians pupping new comedy-panel shows, most of which, sadly, are doomed to be tied in a sack and dropped into the swiftly flowing river of television oblivion. I'm guessing that It's Only a Theory isn't going to make it to adulthood, because it's very difficult to work out what it's for or how it's meant to work. A panel of two gag merchants (Hamilton and Reginald Hunter, who can both be funny) are joined by a celeb guest (it was Clare Balding this week) to offer peer group review on the theories of scientists and experts who quite like the idea of being on telly. They then say whether they've been approved or rejected, though it isn't clear on what basis they arrive at this decision and nobody gives a damn anyway. Last night, they batted around the ideas of a gerentologist who thinks the first 1,000-year-old person has already been born and a psychologist who believes that we shouldn't medicalise sadness - these two topics provoking a meandering and underwhelming blend of flippancy and bland earnestness. It isn't that the machinery doesn't work, it's that they completely forgot to put the machinery in. I can only hope it isn't distracting Hamilton from writing more episodes of Outnumbered.

With It's Only A Theory, BBC4 seem to have taken the unusual step of commissioning a Radio 4 comedy before it's even had a 6.30pm slot. Devised by the reliable Andy Hamilton, whose career takes in Shelley, Not The Nine O'Clock News, Drop The Dead Donkey, Armstrong And Miller and Outnumbered, it sees scientific experts bring their hypotheses to the studio where they are subjected to an interrogation by Hamilton, his regular sidekick, panel-show favourite Reginald D Hunter and a special guest, this week being the blokey Clare Balding. Like most of those Radio 4 shows it is amusing rather than funny and the best lines in this ep are delivered by ageing expert Aubrey De Grey, but it is nonetheless well worth a look.

We always welcome more TV time given over to Reginald D Hunter. Unfortunately, the format's a bit clunky in this new series, which sees Hunter teaming up with Andy Hamilton and special guests to chew over a new theory posited by an expert in their field. Still, Hunter does roll out some gems, with tonight's highlight being an argument between himself and Clare Balding over the virtues of Colin Firth. You can probably guess who wins.