By now you probably all know that the character of Raymond, in the film and now play called Rain Man, is based on a real person with an extraordinary ability to memorise facts – a so-called autistic savant. Robin Herford’s production of Dan Gordon’s adaptation of the original film script is an interesting blend of short scenes with in-depth characterisation.

At least, it would be if Oliver Chris, playing Charlie was not so determined to set a record for rapid line delivery. I appreciate that the opening scene – in which he’s juggling irate calls from people to whom his business owes money, customers who haven’t received their promised goods on time, the rapidly fraying temper of his secretary and the persistence of his girl friend – needs to be frantic, but it would have been good to hear more than mere snippets of the dialogue.

Charlie’s owes are compounded when he discovers that his estranged father has left his fortune in trust. Charlie remembers that he had a (he thinks) imaginary childhood friend – Rain Man; this turns out to be his autistic brother Raymond. From then on it’s a roller-coaster as Charlie tries to use Raymond for his own ends, and Raymond follows his own path.

Neil Morrisey gives a marvellous performance as Raymond, never too obviously playing for the audience’s sympathies – though of course we’re all on his side from the moment his smart white trainers step into the frame. Every nuance of face and gesture – those wondrously splayed fingers, the shoulders scarcely connected to the trunk of his body, let alone its limbs – helps to put a real person in front of us. A flawed being in respect of whatever passes as the norm, yes. But one with whom it is impossible not to empathise.

The pared-down setting by designer Jonathan Fensom reflect the rawness of the characterisations; they are places for people whose feelings are being stripped down. Ruth Everett stands out in the supporting cast as Susan, the girl who will make her own way in the end. Charlie Lawson is Dr Breuner, who has his own, not entirely diasinterested, view of Raymond’s condition and what should constitute his future.