In the old days plays were regularly adapted for the screen, but now it’s much more two-way traffic.

With Ken Loach’s 1970 classic Kes due at the Grand in a couple of weeks, here is an adaptation of the Oscar-winning 1988 film starring Dustin Hoffman and Tom Cruise.

The cases are slightly different in that while Kes was based on a novel by Barry Hines, Rain Man has been adapted by Dan Gordon from Barry Morrow’s original screenplay. In this version with Neil Morrissey and Oliver Chris it certainly works as an engaging and touching piece of theatre.

Chris plays Charlie Babbit, an egotistical yuppie whose business is about to go down the pan when he hears his estranged father has died. The problem is he has left his fortune to Raymond, the long-institutionalised elder brother Charlie never knew (or, more subtly, has forgotten) he had.

Charlie removes Raymond from his care home, initially with the intention of getting his hands on half the inheritance. But when he begins to connect through some long-buried childhood memories during a road-trip from Cincinnati to Los Angeles, a brotherly bond begins to develop.

The production has teamed up with the National Autistic Society, and while it may play a useful role in widening awareness of the condition it may also be open to criticisms for giving the impression autistic “savantism” – Raymond has a fantastic facility with numbers and other data – is more typical than it actually is.

Raymond’s idiosyncratic, birdlike mannerisms, meticulously performed by Morrissey, might be equally unrepresentative.

That said, it would be difficult not to respond to the quiet good humour of the story and the performances, with the ambiguous ending avoiding the obvious sentimental resolution. Morrissey and Chris are excellent, and I also liked Ruth Everett as Charlie’s girlfriend. But some more imaginative design would have lifted the production.

* Running time: Two hours. Until Saturday.