Last Sunday Radios 1, 2, 3 and 4 celebrated their 40th birthdays. Happy bidet to all. Happy serenditipitous moment, too, to those listeners whose hand slipped while they were aiming for the Archers omnibus and ended up with two hours of a Kenny Everett Show on Radio 2 from October, 1981. Cunningly, the station had scheduled it for the actual time when the original had been broadcast, so the timechecks matched. Besides that, there was the unutterable joy of hearing cuddly Ken, who had a thousand better ideas before breakfast on a bad day than Chris Moyles has had in his life. Bliss was it on that Sabbath morn to be alive, but to be middle-aged was very heaven.

In fact, it was quite a week to be a fan of professionalism. Dirk Maggs, the avatar of the sound effect whose radio adaptation of the last three books of Douglas Adams’s Hitchhiker’s Guide to the Galaxy made entirely superfluous the need to read them, returned on Wednesday (Radio 4, 6.30pm) with Adams’s Dirk Gently’s Holistic Detective Agency (motto: “We solve the whole case, we find the whole body”).

With this Maggs officially becomes James Boswell to Adams’s Dr Johnson. Rarely can a technician - nay, artist – have spent so much time and care on reproducing the thoughts of a genius. Multilayered, multifaceted, the sound effects tell a story on their own. What goes on in the background is important – a news report, half-heard, is from “our environment correspondent, Jeremy Clarkson”. An answerphone carries a loop of Ravel’s Bolero. Maggs didn’t have to do that; it’s his little gift to us that he did.

The acting is fine, some of it better than that. Olivia Colman as Gently’s secretary, constantly on the edge of a screaming fit, is wonderful, while Harry Enfield plays Gently as a sort of cosmic Cholmondeley-Warner, and no harm in that, particularly when he bares the fangs behind the smile.

The story should brew nicely over the next six weeks. There’s a murder for a start, and a frame-up, and a missing cat who might not actually be missing. As Gently explains: “Your cat is not lost, his waveform has temporarily collapsed”. It’s a very Adams thing to say. Here’s another one, in further explanation of the “holistic” bit: “We are concerned with the fundamental interconnectedness of all things. Let me give you an example – when an acupuncturist treats toothache he sticks a needle in your thigh. Do you know why? No, and I neither do I. But I intend to find out.”

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