“This is very much avant-garde theatre,” says a man in shorts and trainers, sitting behind a laptop at a conference desk on the stage.  His tongue, of course, is firmly in his cheek – yet this wryly humorous show is indeed experimental, delighting in its deadpan subversion of fashionable theatrical forms.  But there’s substance as well as style to this play, for the real-life story it tackles is a cracking one: a tale of human folly, superhuman endurance, and mortal peril on the sea.

Twelve men have walked on the moon – but by 2012, when the story is set, nobody had ever swum from Scotland to Ireland directly from the Mull of Kintyre.  Longer crossings are paradoxically easier; the shortest route is a uniquely challenging one, torn by harsh currents and guarded by flotillas of jellyfish.  But in the month of the London Olympics, a South African called Wayne Soutter attempted it all the same, in the knowledge that physical failure – the “hitting the wall” of the title – would mean not just humiliation, but possible death.

Actor Tom Williams takes the stage as Soutter, ably capturing the single-minded personality required for such an epic feat.  As his marathon swim progresses and exhaustion sets in, Williams’ Soutter grows truculent and aggressive, overcome by a dogged sulkiness at the impossibility of his own endeavour.  Matthew Warburton, meanwhile, makes a laconic and authoritarian narrator, pushing the story forward with the insistent drive of an especially sadistic sports coach.  The brusque interaction between these two alpha males furnishes a lot of humour – but also hints at themes of companionship and trust, and forms the play’s emotional heart.

To match their uncompromising characters, Williams and Warburton adopt a comically no-nonsense performance style.  Standing beside a utilitarian folding table, they dispense with theatrical details like accents and physicality, making much instead of the bonding experience enjoyed by the audience in the room.  Every now and then, a slyly self-referential remark reassures us that we’re sharing a joke, but this isn’t so much a parody as a conspiratorial wink – the sign of a production which acknowledges the “experimental” tropes it’s playing with, yet still makes effective use of them.

For all its humour, though, Warburton’s script displays a genuine respect for the real-life story, and a nerdy interest in the detail of Soutter’s quest.  While it never feels like a lecture, Hitting The Wall packs in a surprising amount of scientific fact – ranging from the all-important geography of the Irish Sea to the precise reason why it’s difficult to track a swimmer using a flat-bottomed inflatable boat.  There’s genuine tension and drama here, too, for the scale of Soutter’s task is clear, and the outcome of his mission remains in doubt till the end.  As his strength fails – in one of those memorable “avant-garde” moments – the whole audience is involved in a last-ditch attempt to guide the suffering swimmer home.

I am duty-bound to report that the two actors do refer to copies of their script – a cheeky and slightly surprising short-cut, albeit one which fits the style of their performance neatly enough to forgive.  Overall though, Hitting The Wall’s apparent lack of embellishment belies a finely-tuned production, which makes a complex tale accessible and adds a thought-provoking question at the end.  But it’s the ironic, self-aware humour which makes it the complete Fringe package.  Catch it while you can.