It seemed an odd coincidence that twice within a week I should have seen plays that began with the wanderings of a lone little boy and later featured a disintegrating set. First was The Winter’s Tale at Stratford, reviewed elsewhere; five days later came An Inspector Calls, at the Everyman Theatre, in Cheltenham. If one could be said to have influenced the other (and I wouldn’t dream of saying it) then it was certainly Stephen Daldry’s version of the J.B. Priestley classic that must be considered the pioneer in these areas, both boy and set (almost a character in itself) being defining features of this multi-award-winning production.

It is 20 years now since its tentative beginning at York Theatre Royal, before it went on to conquer London and Broadway from a launching pad at the National Theatre, where another of Priestley’s successes, Time and the Conways, is soon to be revived. This reminds me that the ‘time’ element in Inspector – suggested in the stopping of the grandfather clock in the home of the affluent Birling family at the precise moment of the mysterious policeman’s arrival – appears to have been jettisoned by Daldry. Or did I just miss the hands halting on a clockface so far to the back in Ian MacNeil’s amazing set?

The appearance of Inspector Goole (Louis Hilyer) puts a dampener on what had been up until then a happy evening of middle-class complacency. Bluff industrialist Arthur Birling (David Roper) and his pleased-with-herself missus Sybil (Sandra Duncan) were celebrating the engagement of their daughter Sheila (Marianne Oldham) to Gerald Croft (Alisdair Simpson), the son of another local bigwig – a knight of the realm, no less, which Arthur gloatingly confides to his prospective son-in-law he is hoping soon to be as well.

Which is why the probing questions and revelations of Goole are so disturbing. They concern the suicide that afternoon of a young woman, who killed herself by swallowing disinfectant. “What is this to do with us?” is the reaction of those present, but as the questioning continues it starts to seem that all played some part in sealing her fate, including – perhaps especially – the Birlings’ feckless and boozy son (Robert Whiting).

The message of the play (for this is a play designed to contain one) is that we are all (as the inspector puts it) responsible for each other in our society. This was an idea later to be challenged by Margaret Thatcher and her cronies but which was widely accepted in 1945 when the play was written (remarkably in just one week).

Goole’s is the voice of that caring age: dressed in a demob suit of the period and accompanied by an observing chorus of which that lone boy is but one member, he studies and lectures the Birlings as if they were the products of an earlier, crueller era (which, with their clothes and attitudes of 1912, they are).

Then the lights go up, and he turns to address us, the audience of 2009, with his call for kindness and compassion. Truly, Daldry transformed this once creaking stalwart of the amateur stage into a timeless piece of theatre. Long may it continue to be revived.

An Inspector Calls is at the Everyman until Saturday. It tours to Milton Keynes Theatre between April 28 and May 2, and is at the Oxford Playhouse from June 9-13.