Secret Theatre: ten actors, seven shows – and an entire network of theatremakers of all kinds clubbing together to make it happen. It is one engine ignited and driven by artistic director Sean Holmes and it has built grippingly dynamic, future theatre. It has been cemented into place over a period of two years (during the shiny new overhaul of the Lyric Hammersmith), then paraded up and down the country, memorably becoming the word on the cobbled and puddled street of the Edinburgh Fringe. And that word circulated around A Series of Increasingly Impossible Acts in particular, promising to be an absolute eye-opener by throwing in our faces the definitive meaning of ensemble. This weekend was the culmination: the grand finale of Secret Theatre. All seven skill-exasperating shows presented in one solitary weekend.

I saw the final show of day one, A Series of Increasingly Impossible Acts, doing exactly what it says on the tin and loads more besides, exhausting its protagonist as it goes. The premise is simple enough: a protagonist is elected by the audience and from then on is responsible for two things: 1) to attempt to overcome a series of impossible acts and 2) to improvise.

But it’s not simple, not even a little bit, especially not for that evening’s protagonist Leo Bill, whose earnest and compassionate performance was matched by his effortless wit. Bill was battered and bruised before he even started. By the time he’d been stripped, wrestled by a man twice his size, eaten a lemon and been harassed out of his own skin, blood had begun to seep from his knee and his brain was battered and yet he was elated and relieved. Like it had all been worth it.

And it had absolutely all been worth it. A Series of Increasingly Impossible Acts is unpretentiously the bare bones of theatre. The audience participates naturally as the actors seem completely themselves, there are no bells and whistles over-gilding the staging. Bill goes through a Total Wipeout-esque assault course of universally applicable impossibilities. He answers from lists of questions improvisationally with exhausted instinct. It’s strenuous and honest, two constants in a show that would have been entirely different with a different protagonist or even just on a different day. A Series of Increasingly Impossible Acts is extraordinary because of its normality: it shows us familiar struggles and hurdles that develop as the protagonist deciphers what his show is about as he goes along, firmly placing himself on a level with the audience.

Ultimately we are shown that everyone’s life has different obstacles and curve balls but we end up drawn together because we all endure them. The impossibilities that get chucked in our direction now and again are made harder by opposition or easier with help from each other. That’s true of anyone and Secret Theatre makes us realise it so innovatively, bewildering and entertaining us in every way they know how.

A Series of Increasingly Impossible Acts is played at Lyric Hammersmith. For more information and tickets, see the Lyric Hammersmith website.