It’s the late 1960s, when telephones still had dials, and — as Greg reminds us — it cost a pre-decimal fourpence to ride on a London bus. Greg has moved into Ginny’s flat, and into her bed. It soon becomes clear he has no experience of living with a girl at close quarters — he gets quite bashful when called “a fantastic lover”. But why is there never anyone on the other end of the line when the phone rings? Why are there so many flowers in the flat, and so many boxes of chocolates stuffed into drawers? And why is Ginny so reluctant to let Greg meet her parents?

Greg and Ginny inhabit Alan Ayckbourn’s classic Relatively Speaking. Premiered in 1967, the play is a thoroughbred example of Ayckbourn on top comic form, not least at the moment when Greg — fed up with Ginny’s prevarications — decides to travel to rural Buckinghamshire (cheap day return: 19 shillings and sixpence) to find her supposed parents for himself. In spite of many awkward pauses, stilted remarks about the weather, and strange conversational non-sequiturs, Greg fails to realise that Philip and Sheila, the middle-aged couple he meets at The Willows, Lower Pendon, have no daughter at all, let alone one called Ginny. All this is hilariously observed in Orla O’Loughlin’s production for the Watermill, Newbury. Every time there is an awkward break in the conversation in Philip and Sheila’s garden, the birds obligingly pipe up and chirrup more loudly. In desperation, Greg is asked to stay for lunch, given an apron, and put to work in the kitchen. Sherry is offered: “Sorry there’s no gin-ny,” says Philip, with a forced laugh. The laboured pun is entirely lost on Greg. Ayckbourn and O’Loughlin are well served by the Watermill cast. Greg Haiste (right) has a whole array of bewildered expressions on display as Greg, who is plainly a nice chap, even if not greatly endowed with brains. Behind her big smile and gleaming teeth, Ellie Beaven’s Ginny is both evasive and manipulative. David Acton and Gillian Bevan as Philip and Sheila have everyday domestic bickering down to a fine art — “Where have YOU put the garden hoe?” asks Philip irritably. But he becomes convincingly more belligerent and sarcastic as certain unfortunate facts begin to surface.

Having been a 1960s London flat-dweller myself (I confess), I find Anthony Lamble’s period set designs ring absolutely true, in a production that zips along. This is just the show to brighten a dreary winter’s evening.

Watermill Theatre, Bagnor, near Newbury, until March 26. Tickets: www.watermill.org,uk or 01635 46044.