The idea of it is much better than the theatrical reality, which is not as good as the reading I heard on the radio: arts journalist Jasper Rees walks out of his marriage and picks up his horn after 25 years.

At a convention of horn blowers he takes on the challenge of performing a Mozart concerto he stumbled half through (before passing out on stage) at school and sets off to limber up his lips and practise his trills and arpeggios.

It’s a simple, touching story – though, coming immediately after the devastating Tolstoy monologue at the Gate, you do wonder a bit about the poor wife he left behind and what is this Jasper bloke really like – and it’s performed with brio by Jonathan Guy Lewis on a bare stage with basic props and a constellation of French horns.

Guy Lewis plays all the stops and rips out his characterizations of Jasper’s coarse-grained horn guru, a pair of creepy tutors at an American horn camp and alludes to a potted history of the repertoire and some of its most distinguished interpreters.

But the more Guy Lewis strains, the less beguiling he is, until, frankly, he’s not beguiling at all. He may well be horn mad, like Ford in Merry Wives, but his condition is unfortunately not contagious. Harry Burton’s production is lit – how odd is this? – by Jeremy Coney, the former New Zealand cricket captain, and the sound by Daniel Thomason, which assembles snatches of  Handel, Sibelius and Wagner, is only patchy, and never blasts you to the sides of the theatre.

I think this is because the writing is witty but bitty and there’s no accumulation of theatrical texture, even when Guy Lewis takes the stage again at the annual convention for his date with destiny, sweating like a pig and breathing like a terminal asthmatic.

The horrid truth is, though, that he doesn’t play particularly well, although of course it’s jolly good that he plays at all. In one of their songs which was set to the best known Mozart concerto, Flanders and Swann lost their horn; in effect, found it “gawn”. Jasper found his, but as far as the stage version of his memoir goes, it’s still touch and go.