“Laughter is the best medicine. I believed that until I got diabetes.” As delivered by Bobby, a washed-up vaudevillian confidently embodied by Les Dennis, this gag is funnier than it looks. Similarly, you have to witness it to appreciate the sleek effectiveness of Danny Robins’s new play, which seems to be about comedy, but is surreptitiously concerned with giving Brexit Britain a spanking. Bobby lives in slippered seclusion in his tatty Blackpool flat, his semi-racist banter now a historical curio. His son Michael (Blake Harrison) is the anodyne new face of comedy: a kind of stingless Russell Brand, whose career is jeopardised when he drunkenly punches a young Bangladeshi (Nitin Ganatra, owning the stage). As chance would have it, his victim harbours ambitions to be a comic and blackmails Michael into giving him five minutes on his primetime slot. The tour de force that follows shows up the hypocrisy of Michael’s right-on routine while shining a torch into the eyeball of our own race-based assumptions. Boom, boom.