J.B. Priestley’s An Inspector Calls is a phenomenon. For long staple fare at provincial repertory theatres, in 1989 director Stephen Daldry was invited to take a fresh look at the dear old piece. The resulting production made him a millionaire, and 20 years on still grips mightily.

Arthur Birling (David Roper) is celebrating. A self-important industrialist, you are frequently reminded that he is an alderman, a JP, and knows the Chief Constable personally. Now – shhhh – a knighthood could be on the way, and his daughter Sheila (Marianne Oldham) has just got engaged. The family seems larger than life, for the celebrations are taking place in their giant dolls house of a home – even though the drawing room is two storeys high, their heads almost touch the ceiling. The superb set design (Ian MacNeil) is crucial to the production.

The house is mounted on stilts, and in a clear class distinction, down below toils servant Edna – she’s played by Diana Payne-Myers, a former dancer who knows exactly how to make her emotions clear without ever speaking a word. Also down below is Inspector Goole (Louis Hilyer), who has come to question the family about the suicide of a young girl, sacked from the family firm some years before. “Whatever has it got to do with us?” the very strange inspector is asked with varying degrees of rudeness.

Most unusually for a production 20 years old, director Daldry is still in charge. The original, emphatic, acting style is preserved: indeed cast members are encouraged to emulate their predecessors. Thus, Sandra Duncan, as Arthur’s imperious wife Sybil, is a dead ringer for Barbara Leigh-Hunt. At the end, the Birling family are left thoroughly unsettled. And so was I: could it be that Daldry has not only brilliantly revitalised an old warhorse, but also treated us to a gigantic send-up of old-time rep acting, with its deliberate speech and heavy mannerisms?

The play continues until Saturday. Call 01865 305305 (www.oxfordplayhouse.com)