Kenneth Branagh and Rob Brydon revive their odd-couple hijinks for this fourth production in Branagh’s Garrick season: Sean Foley’s adaptation of Francis Veber’s classic 1969 French farce.

Branagh is a suave hitman who just wants to be left alone to complete his job: assassinating a witness at the courthouse opposite his London hotel. But in the adjoining room is Brydon’s sad-sack photographer, suicidal after his wife left him for her therapist. When the killer is forced into a life-saving role in order to avoid the authorities, chaos ensues.

It’s goofy throwback stuff, from the dropped trousers and comedy amnesia to people caught in uncompromising positions and having doors slammed in their faces. Foley’s 90-minute piece, which he directs, keeps the gags coming, though it plateaus with unconvincing introspection rather than climaxing. The combination of contemporary references with seventies sitcom sensibilities also jars. Yes, wild improbability comes with the farcical territory, but become completely unmoored from reality and the slapstick loses its dangerous edge.

Branagh and Brydon make an entertaining double act: one simmering with menace, the other a blithely babbling chump. Brydon bares all, both physically in eye-wateringly skimpy pants and emotionally, making us root for his “one-man disaster zone”, while Branagh provides a studied but impressive physical tour de force following a medical mix-up, staggering, straining, keeling over like a felled tree, and discovering his inner Michael Jackson.

It’s thin fare for the supporting cast – Marcus Fraser’s policeman trapped in a wardrobe, Claudie Blakley’s ex-wife spouting tiresome malapropisms, and Alex Macqueen’s shrink a one-note rage monster. Mark Hadfield fares best as the camp, increasingly panicked porter. Alice Power’s chintzy boutique hotel design gives us mirror-image rooms and an illusory divide – an effective visual in a slick but ultimately inconsequential production.

Rating: 3/5 stars.