Unfortunately John-Luke Roberts can't be with us today, but in his place he's sent famous medieval poet Geoffrey Chaucer… who's not a bad stand-in to have at your disposal, even if he isn't a big fan of clothing. Chaucer – being from the past, of course – speaks in his favoured Old English (or is it Onglish?) This takes a little getting used to, but after a few minutes you catch on and it soon becomes addictive.

The 14th-century raconteur brings his past-perspective into a modern world he doesn't understand, in an eclectic show that spans the entire breadth of time itself. Roberts seems hell-bent on becoming significant and this piece, as abstract and tongue-in-cheek as it might be, has enough depth and originality to put that particular Holy Grail well within reach. For one thing, it's nothing short of impressive to have the audience going along with such an odd concept – to the point that those selected to participate even start responding in Mediaeval language (or longwij, as it were).

Roberts is a blistering alternative fringe act in his prime, who takes us on a hilarious and meandering journey through the present into a very real future. He mourns the demise of planet Earth via a bizarre but, I would say, necessary mix of character-led stand-up, fortune-telling and an appearance from a famous popstar facing a crisis of self (with some imaginative use of costumes along the way). As clever and philosophical as it is bonkers, at times during this performance, it seems Earth's only hope is if we send Roberts along to the next worldwide climate-change gathering to perform his floating space-head routine. Only then will humans atone for their poor choices.

It's one thing to joke about crowbarring a message into a comedy show; but when Roberts does just that, then leaves the audience lauding it as an absurd masterpiece that fulfils its intended message, you know you have witnessed something special. And there's no denying that the vivid imagery and thoughts devised here stay with you long after the performance. If John Luke-Roberts has set out to change the face of stand-up as we know it, mission complete. This is an exciting, layered piece of comedy; this is significant.