'What If If Only' review - Caryl Churchill's newest play proves small can be mighty

In between two mammoth outings (The Normal Heart at two hours 45, Hamlet at three hours 15), I caught Caryl Churchill's new play What If If Only, which is roughly the length of the interval of those epics. In fact, it was due to be even shorter - it's gone up to 20 minutes from the originally announced 14 - but the indomitable Churchill proves that small can be mighty, particularly when your work is so innately, and potently, theatrical.

The opening stage direction is simply "Someone on their own", and indeed when we first meet that Someone, he's in an overwhelming state of solitude; John Heffernan makes him an open wound. His unnamed partner has died, and yet he is still talking to them, still one of a pair. The relentlessness of grief comes rushing through in his inconsolable repetition: "I miss you I miss you I miss you I miss you. I miss you."

And then he is no longer alone, but the visitor is an unexpected one. Played with comical yet unnerving joviality by Linda Bassett, she is the Future - or at least a potential one. She heard his longing: if only things were different, what if we had made different choices. Well, if he can make her "happen", she can give him another world, one where he might be reunited with his lost love. Her version, she insists, is "equality and cake and no bad bits at all."

There are shades of Constellations in this romantic slant on the multiverse, mixed with a metaphysical ghost story. As Someone vacillates over the possible other timelines, he inadvertently summons them forth. And, in a spine-tingling turn, Bassett plays them all, these competing Futures - young and old and large and small, eager and angry and pleading and frightening. It's like Jonathan Pryce's famous Hamlet, where he was possessed by his father's ghost, times 100.

James Macdonald's note-perfect staging places Someone in a white cube, and, via Miriam Buether's design and Prema Mehta's lighting, gives Bassett multiple shadows that seem to take on a life of their own. It places us in the same hallucinogenic headspace as Someone.

It's not just a tour-de-force performance, though. It gives us the eerie sense that all these competing possibilities are part of the same whole, with one rising to the top perhaps by chance - and that it could so easily have gone another way. We have all pondered that sentiment over the past year (if more prosaically), trying to make sense of the unfairness and arbitrary nature of the pandemic, the terror that comes with the unknown.

These other futures also contain varying global realities, Churchill's script touching on war and the environment, nuclear power and robots. It builds from a personal choice to an immense responsibility, from grief as the overwhelming entirety to one strand of many. There is hope, too, from the no-nonsense Present (also Bassett) asserting itself with a bright "hurrah hello...I'm here now" to a determined Child Future.

As ever with Churchill, the meaning of her work probably isn't that simple; like the multiverse, there are infinite possibilities for interpretation. Beautifully, sensitively, Macdonald's production honours that ambiguity: while the staging is crisp and exact, the emotion palpable, it leaves space for the worlds that an audience brings to theatre.

The Royal Court has 6pm and 10pm performances of the show, so you can easily pair it with Aleshea Harris's Is God Is or Lucy Kirkwood's Maryland. But equally, Churchill supplies more than enough to chew over during a pre- or post-show meal, and long after.

What If If Only is at the Royal Court to 23 October.