Complicite’s new venture tells the story of an Indian mathematical genius, Srinivasa Ramanujan. He is the kind of figure who might feature in a worthy but slightly dull Horizon programme. But this isn’t telly; it’s theatre – and Complicite does theatre as flamboyantly theatrical as it can be without becoming annoying, and with a swaggering disregard for the supposed gulf between art and science.

Ramanujan appears to have had no personal life – no close friends, no lovers, no sense of humour. You might think this would limit the drama a bit, but there is something genuinely romantic, even tragic, about his life. One day in 1913, a Cambridge maths don, GH Hardy, received a letter. It was the kind of loony letter he received frequently, dense with formulae and claiming to have devised astonishing theorems. The writer was a clerk at the Madras Port Trust, with no university education. Yet, as Hardy examined it more closely, he realised there was something extraordinary there.

After much persuasion, Ramanujan sailed for England and took up residence at Trinity College, wearing slippers and existing on a diet of rice and carrots. There, he continued to produce brilliant, baffling, inexplicable work for five more years until, increasingly ill, he returned to India, where he died in 1920, aged 32. Many of his discoveries are only now being understood, proving invaluable in such fields as string theory.

Complicite enriches its version, “conceived and directed by Simon McBurney” and further “devised by the Company”, with a present-day couple connected to the story of Ramanujan: Ruth, a maths lecturer, and Al, an American futures dealer. Their sweetly faltering romance and marriage is the play’s emotional heart, since not even the wildly inventive Complicite can make Ramanujan more than intellectually compelling.

Praise is due for the company’s efforts to make us do the math. The lives of boffins according to Hollywood are all soupy emotional torment, with the intellectual stuff taken out in case it frightens the audience (as in A Beautiful Mind). Complicite is having none of that condescending tosh. Here we get full explanations, by Ruth, of some fairly gritty numbers.

You are reading the words of someone who failed maths O level. At the time, I believed it was because I had an artistic temperament. Actually, it was because I was lazy and stupid. But I was quite excited to learn from Ruth what partitions are, and that the number 200 has three million million million of them.

The pleasure of sitting in a theatre and amassing pure and useless facts is not to be underestimated. Indeed, I was struck again by what a good medium theatre can be for expounding hard maths and science. Think of Michael Frayn’s Copenhagen or Terry Johnson’s Insignificance.

A Disappearing Number could have ended up a terrible mess, but, as well as inexhaustible originality, Complicite has those equally vital qualities control, clarity and purpose, so the play never falls into fractured, effects-ridden theatricality that quite literally loses the plot. The use of the overhead projector to show Al’s hands, hugely magnified on the back screen, is a haunting moment. There is a constant, beautiful slow-mo snowfall of numbers down over the darkened stage, and we see some gorgeous video clips – of taxi rides in Madras, landscapes of southern India and England, seascapes of water and moonlight – done with a truly painterly eye by the designer, Michael Levine.

The peripheral material is often stronger than the central story, such as the wonderful exchanges between Al and his BT customer adviser, “Beatrice” at “BT HQ” – actually Lakshmi in Bangalore. Their telephone relationship moves from anger and frustration (credible) to something resembling actual human interchange (incredible, but very touching), and it is one of the evening’s many glittering highlights.

Underlying these echoing stories and symmetries are tentative suggestions of the finite world, shot through with infinity and intimations of immortality. Two deaths close the play, both movingly done and both hinting that the play isn’t closed at all.

Barbican, EC2

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