Those artful jokers at Told By An Idiot are entering dangerous ground with My Perfect Mind, a unique retelling of how ultimate thesp Edward Petherbridge suffered a stroke during rehearsals for his eponymous role in King Lear. Less of a ‘play within a play’, and more of a ‘play torn up and thrown back to stain the wall while the players narrowly avoid falling into the trapdoor’ firecracker of a piece, My Perfect Mind shows how daring this company is as it brings Told By An Idiot’s signature sharp-witted silliness back to the home ground of the theatre.

In this surrealist meditation on performance, reality, madness, tragedy, modern art, travel and life in the ‘thee-ay-tahr’, Petherbridge returns to tread tilted boards and tell his own story. Joined on stage by the thrillingly versatile Paul Hunter, the septuagenarian – now fully recovered – travels through the muddled pages of his biography, attending rehearsals at a New Zealand playhouse, meeting his mother two days before his own birth, consulting with doctors in an oh so very different type of theatre, and returning to the pavilion of his hometown in the body of an experienced actor. Here, in a scene that may strike a chord to those who still dream about school maths exams, elderly Petherbridge gazes nervously out beyond the theatre lights and offers, in a childish voice, a medley from King Lear.

Opposing this shy youth, we have Petherbridge in full swing, an assertive cloud of scarf-swishing, ‘darling’-calling, anecdote-sharing and name-dropping. In short, a luvvie through and through. In this world, Noël Coward is dipped right into the kitchen sink, a semi-colon is egotistically interpreted as “Shakespeare’s sweet way of reminding me that I need to breathe”, a melancholy actor must be out of work, and a missed opportunity to snack on a biscuit is turned into an occasion to brand mime as “such an unsatisfactory medium”. The gags are well-engineered, and faultlessly delivered by Petherbridge and Hunter, but there’s a certain smugness to how many of the jokes seem to test the audience’s knowledge of the stage and – at moments – run the risk of being too submerged in the world of theatre.

Thankfully, in true Told By An Idiot fashion, nothing is taken too seriously. While Petherbridge ostentatiously muses that the show “either looks slapdash or pretentious”, Hunter, a tremendous comic actor, takes the role of Lear’s jester to ensure that the first of these two options is firmly taken care of. Aware of the limitations of playing all of the secondary characters in this biography in a mere 90 minutes, Hunter relishes the art of caricature and brings to the stage a reel of characters that all toy with the idea of ‘borderline offensive’. We first meet him as he exchanges his Ws for Vs to take on the part of the German professor who explores Petherbridge’s condition – but he’s also the taxi driver who takes our troubled Lear from New Zealand to Bradford, the housekeeper with a PhD in Shakespeare, the Kiwi artistic director engaged in a violent battle with Russell Crowe over royalties, and Sir Laurence Olivier, taking a break from playing Othello – ink still circulating his face in a satirical nod to what wasn’t considered ‘borderline offensive’ in 1964.

This fragile and utterly madcap narrative is held together with control and cohesion by director Kathryn Hunter who, as the first female British actor to play King Lear professionally, no doubt has a story or two to tell about taking this part. Though it may mock the industry, the most beautiful interactions occur when Paul Hunter settles in the role of actor. While chatting to this fellow cast member before a show, Petherbridge relates the more abstract episodes of My Perfect Mind as small talk – his battles with movement, expression and ink in a lecture room full of medical students becoming, in the retelling, a casual episode no more out of the ordinary than having a jog. Triggered by a King Lear – one of our most celebrated plays, and one where madness is most firmly interrogated – theatre steps up as the place where any sense of instability can be explored and rationalised. Sure it’s mad, but it works.

My Perfect Mind is playing at the Young Vic until 27 September. For more information and tickets, see the Young Vic website.