Duncan MacMillan started writing ‘Lungs’ ten years ago. Apparently he intended to write a big play about climate change and ended up writing a small, intimate play about a young couples personal anxieties as the world warms up around them. Post Greta Thunberg and with Claire Foy (Elizabeth) and Matt Smith (from Netflix ‘The Crown’) available, this was surely the right time for ‘Lungs’ to return.

The play opens with a classic row in the IKEA queue as the possibility of having a baby is raised for the first time. MacMillan’s script juxtaposes all the big relationship conversations between this earnest, middle class couple in chronological order so that the actors literally leap from twenty somethings to old age in an athletic show of performance agility. Set in the round and running straight through at 80 minutes, this is a seriously stripped back production so there is literally no-where to hide. From joy to despair in a milli-second, Foy has a chance to unleash the tight-lipped Queen that’s made her name and Smith has the ordinary posh boy, slightly in awe of his clever woman (but yet to grow up himself) down to a tee. There’s no doubt both actors are up to the task in hand.

Designer Rob Howell’s minimalist set only provides a crust of crystalline rock for each character to perch on at either corner of the stage space. The characters are dressed in muted dungarees and trainers – dropping t’s in otherwise cut-glass accents. She is doing a PHD, he is an unsuccessful musician (soon to get a proper job) she appears to suffer from generalised anxiety disorder, and he seems paralysed by her verbal outpourings. But, this is a generation that are used no filter sharing and apparently they love each other.

As ‘Lungs’ progresses it loses its crisp observations, rushing to the end without gaining much of foot-hole on their latter years. For such a specifically ‘modern’ couple, the sexual politics are unsettling – the female character certainly dominates, though not because she is strong but because of her relentless torrent of doubt. He inevitably fails her through testing times (when trying to have a baby) and things only work out between them when he eventually plays the old-fashioned male and tells her he will look after her and everything will be OK. It’s certainly a relief when she finally stops talking.

The beauty of ‘Lungs’ lies in the moments where their hypocrisies are teased out through their witty repartee and externalised, internal dialogue. They keep reminding themselves that they are ‘good people’, they recycle after all and seriously consider planting forests to offset the carbon footprint of their unborn child. There are many original and sharp moments of humour but how much you enjoy the show probably ultimately depends on how much sympathy you feel for the duo.