Normally I detest the programmes in BBC Radio 4's post-Six O'Clock News slot, a so-so procession of creaky panel shows (you know the ones I mean) and lame comedy vehicles for Oxbridge types who can't get on the telly.

There are honourable exceptions, though, and Chain Reaction (Wednesday, BBC Radio 4, 6.30pm) is prime among them. If you're unfamiliar with the format, Person A interviews Person B, then the following week Person B interviews Person C and so on.

The returning series kicked off with Adam Buxton talking to League Of Gentleman's Reece Shearsmith, which was tasty enough. But then Shearsmith took on Bob Mortimer, and this week Mortimer took on... who else but his long-time comedy partner Vic Reeves? Whether through chance or design, the day before the programme aired the pair announced their first tour together for 20 years, kicking off in Glasgow, no less.

Introducing him as his "comedy hero", Mortimer's first question was "Have you ever been to Whitby?", though by that point Reeves had already pulled the carpet from under his partner's feet by telling the listening audience that Mortimer was wearing only "the tiniest little Speedos" and, round his neck, a bus conductor's ticket machine. As he intended, it was an image that was hard to shake for the rest of the programme.

And had he been to Whitby? Yes he had. Cue a story about visiting the Dracula Experience, the Abbey, the harbour and Maggie's Fish And Chip Restaurant.

"Can you remember when we first met?" Mortimer asked a little later.

"Were we working on the same cruise ship?" Reeves countered. "I think we were both shovelling coal."

Before long we'd descended into another piece of inspired tomfoolery, one which had Pat Nevin joining the Apollo 11 crew while Reeves lifted the rocket on its launchpad using only his bare hands. After the question "You're often mistaken for an MP. Would you like to tell us about that?" Reeves confessed that it was true and that he was also often mistaken for former jockey Lester Lester Piggott. "Usually when I'm kneeling in church," he added. "They pat me on the head for good luck."

This was laugh-out-loud funny from start to finish - and it's not often I can say that on a weekday teatime.