Above all, it is amiability that seems likely to carry Rudy’s Rare Records to box-office success. First, there is the good nature that Lenny Henry extracts from an audience. On his home patch of Birmingham this is so palpable that it’s almost an extra character on stage. Gusts of goodwill greet him whether he’s doing a goofy rasta turn or making sullenness look rather touching. Then there is the sympathetic nostalgia of Danny Robins’s script which, based on a Radio 4 comedy series, comes with a ready-made fanbase.

Rudy’s Rare Records is a haphazardly run music store which doesn’t so much sell vinyl as scatter it about for browsers: “What’s not on the shelves is on the floor.” Its business is under threat from Amazon; its structure is under threat from a property developer; its staff look back on threats from racists. There are plenty of occasions to drum up support, and plenty of occasions for someone to take to the floor with a burst of reggae or rap.

The turns, fuelled by a band half-hidden at the back of the stage, are the high spots of the show: luscious wiggling from Lorna Gayle, moody huskiness from Larrington Walker, sharp vigour from Joivan Wade. Otherwise, there is little to startle; much to reassure. The human pivot of the plot is the same relationship that propelled Steptoe and Son, Till Death Us Do Part and Ab Fab: the squaring up of unbuttoned older and aspirant younger generations. Walker likes to loll around in his vest; Henry likes croissants. The jokes, which come pell-mell, breaking off only for some dad-and-son syrupy stuff at the end, don’t have much bite but Paulette Randall’s production, headed for Hackney Empire, communicates wistfulness as well as a few beams.

Rudy’s Rare Records is at the Birmingham Repeterory Theatre until 20 September, then at the Hackney Empire, London E8 from 24 September to 5 October