The last time Claire Foy and Matt Smith played opposite each other as a couple was in The Crown. She was Queen Elizabeth and he was Prince Philip.

This time the actors are reunited by Duncan Macmillan’s 2011 play as nameless, modern day cohabitors who we first encounter as they queue in Ikea which is where he pops the question about trying for a baby.

This triggers a conversation that is brimful of age-old anxieties that go with having and raising a child such as money (he’s a struggling a songwriter) and the physiological change that bodies go through while pregnant, not to mention the pain of giving birth.

But despite its age, the worry that makes this work a play for today is that of climate change. 

It was by no means the only attempt in 2011 to address global warming. The National’s disastrous, multi-authored Greenland comes to mind, and so does Richard Bean’s infinitely better The Heretic which addressed global warming denial. 

But whether the plays were good or bad, the issue they addressed back then felt more like something that should worry us rather than actually did. Not now.

These days you have to be a saddled with Trumpian levels of ignorance not to know why it was that Finchley Reform’s Rabbi Newman got himself arrested while praying in – and blocking – a street near the Bank of England during the Extinction Rebellion protests. 

This revival, directed by the Old Vic’s Matthew Warchus, suggests that Duncan’s play is the best of that bunch. It is deeply informed by the urgent issue of global warming though without being preachy about it.

Cleverly, its heroine is working on a PhD about climate change, which gives the couple easy access to the frightening facts and figures about the crisis without making them look like environmental evangelicals.

A child produces a higher a carbon footprint greater than seven years worth of flights to New York. She tells her partner. “I’m giving birth to the Eiffel Tower.”

But the source of the play’s energy is the way in which that conversation started in Ikea becomes the driving force throughout Matthew Warchus’s simply staged production of 80 uninterrupted minutes.

Without missing a beat the conversation takes us through time, multiple locations and the couple’s crises. And against these highs and lows of personal drama the planet is a constant — or rather its inexorable decline is.

The writing is funny and stacked with cracking one-liners. Especially well observed is the way in which men can be illiterate when it comes to reading women in the grip of hormonal and emotional effects of pregnancy. And here Smith superbly conveys a deadpan lack of understanding.

But the production’s heart lies in Foy’s deeply moving performance - a portrayal of a woman conflicted by the knowledge that what she wants most in our world is probably probably what the overpopulated world needs least.