As an example of politically committed theatre in Brechtian style Earthquakes in London, which Headlong first staged last year at the National Theatre, is unusual — refreshingly so — in avoiding the hectoring tone usually associated with the genre. Its concern, in large part, is global warming, a subject that is contentious only to those who value the opinions of a clutch of bigoted fogeys over the informed judgment of scientists.

Playwright Mike Bartlett’s view is clearly that disaster is coming, unless our mode of life is drastically altered. An odd feature of his play, however, is that the character who principally argues the point — though Kurt Egyiawan’s Eritrean student Tom plays him a close second — is a celebrated scientist who is both potty and deeply unpleasant.

Robert (Paul Shelley) is the father of three very different sisters. Only some way into the slightly overlong (at three hours) production do we learn the precise nature of his strange relationship with them, and of the monstrous proposal he has made to his middle daughter, pregnant teacher Freya (Leah Whitaker).

It emerges, too, that as a young man (now played by Joseph Thompson) he has been tempted by the blandishments of a pair of aviation industry slickers eager to buy from him the opinion they wish to hear. This greaseball duo, played by Ben Addis and Gyuri Sarossy, look the part with their seventies’ wide lapels, flared trousers and sideburns, but as careful a director as Rupert Goold ought not to have marred the period feel by permitting them to introduce irony through the use of air-drawn inverted commas — very much a 21st-century thing.

The production features a doubly revolving set (Miriam Buether) which allows dramatic episodes to overlap and sometimes proceed simultaneously. There is excellent use, too — in epic theatre tradition — of original music (Alex Baranowski), including a chirpy number for the full company and a comic ditty for four peroxide-barneted, pram-pushing, upper-crust ‘Stepford wives’.

Motherhood is a central theme of the play, in the matter of whether ours is a world in which anyone would wish to raise a child. But there is much else to enjoy in the bang-up-to-the-minute presentation of Robert’s eldest daughter Sarah (Tracy-Ann Oberman) as a savvy Liberal Democrat environment minister in the Coalition Government and his youngest, Jasmine (Lucy Phelps), as a drug- and sex-hungry 19-year-old student.

There is interest, too, in the characters of the elder sisters’ good-sort husbands (John Hollingworth and Seán Gleeson). I was baffled, though, over why Sarah’s Colin (Gleeson), having been introduced into snappier dressing by Jasmine, should have referred to what was visibly an utterly mismatched jacket and trousers combination from Liberty as “a suit”.

Even more puzzling is the transformation of Helen Cripps from a show-stealing 14-year-old boy pupil of Freya’s — “I register very high on the autism spectrum” — into Freya's now grown-up daughter on a mission to save the planet.

This enjoyable and ambitious production continues until Saturday. Tickets: www.oxfordplayhouse.com or 01865 305305.