RADIO / Hidden laughter: Robert Hanks enters Lionel Nimrod's Inexplicable World

'Since the dawn of time,' runs the introduction to Lionel Nimrod's Inexplicable World (Radio 4, Thursday), 'every man has cowered in shame before that which he cannot comprehend.' True enough - hence, you will find no attempt here to analyse Jimmy Young's popular success over a quarter of a century of broadcasting (as celebrated last week on Radio 2).

Lionel Nimrod itself is easier to grapple with. A new comedy series fronted by Richard Herring and Stewart Lee, two of the writers of On the Hour - which ought to be pedigree enough - it takes as its starting-point the genre of pseudo-documentary that concerns itself with pseudo-science: parapsychology, the lost world of Atlantis, crop circles, that sort of thing. 'Join me - if you dare - in this, my inexplicable world,' invites Nimrod in a voice apparently resonant with the horror of the unknown but which is in fact Tom Baker with the echo turned up high.

But the generic spoofing in this first episode - dealing with monsters, fairies and UFOs - only provided a minimal framework for a sequence of tangentially related sketches and jokes, some sharply satirical, some trying for laughs simply by surreal juxtaposition, some just corny. The wild variety in style and quality, which in an ideal world would create a sense of uncontainable zest and inventiveness, actually suggests that they haven't worked out thoroughly what they want to do. It isn't just that there is no single, stable target, but that they change their minds from minute to minute about what might constitute a hit.

Part of the trouble is that Herring and Lee (a week is too soon to be sure which is which) are not confident enough as performers, so that you find yourself landed halfway through a joke with the distracting worry that the punchline isn't going to work. A lot of the time you're laughing less at what you're hearing, than at what you think they're getting at (such as the sequence in which a kidnapped Daryl Hannah, 'star of the documentary film Splash', is confined in a tank of water to make her turn into a mermaid). The material is a little repetitive, too - the Cyclops that confronts Odysseus introduces himself as Ian; a member of an alien invasion force poised to conquer the planet insists on being addressed as Simon.

But it gets by on sheer likeability - it's easy to let the dull bits pass because, well, they seem like such nice boys. And then you're rewarded with such imaginative notions as the Solihull vampires who have a supportive circle of accident-prone friends to keep them supplied with blood; or Peter Fenn's Hammond Organ 'Believe it Or Not' File - 'Believe it or not, at breakfast time in the Fenn household, 'UFO' stands for 'Unidentified Frying Object'] ' Mr Fenn's astounding facts are recited to a Hammond organ playing 'Up, Up and Away in my Beautiful Balloon' ('Beautiful balloon - beautiful tune'). Inexplicably, it works.