Kit Redstone is in a doctor’s examination room, waiting for the doctor to finish nattering about his supper. Then Kit pulls down his trousers, revealing the top half of his rear end. The preoccupied doctor sinks the sippy cup end of a sports water bottle (a versatile prop) into an expectant butttock.

This is Kit’s first injection of testosterone, and it is not going quite as ceremoniously as he’d like. Rewind: the doctor plunges in the bottle teat, before Kit is borne aloft by a posse of rollicking men, spun around the stage in a rapturous, all-singing, all-dancing ceremony of rebirth. From this day forth, Kit will be a fully fledged man.

Not.Testosterone is the story of Kit’s transition to a man over the two years prior to the production, told through his first visit to a male changing room, interwoven with flashbacks and fantasies. This particular fantasy provides one answer of many to the question: “When did I become a man?” But of course, becoming a man is not as straightforward as a few seconds with his trousers down. After all, what makes a man?

Kit has collaborated with Rhum and Clay company, comprised of artistic directors Julian Spooner and Matthew Wells, who trained at Jacques Lecoq – and it shows in their incredibly polished performances. Playing a variety of interchangeable male figures, their every move is finessed, so that they become stylised versions of masculinity, all swaggering machismo, unable to discuss their feelings, cry, or touch (except when playing sports together, in pack formation); they are archetypes or comic strip characters, without the depth of reality.

Kit’s performance, on the other hand, is of raw authenticity: he sings with a fragile, untrained voice and misses his dance cues. These contrasting styles allow us to see Spooner’s and Well’s personas through Kit’s perspective: born and raised as men, they seem to flawlessly inhabit their masculinity, and Kit is an eager apprentice to their expertise.

Staring in the mirror that sits across the back of the changing room, Kit is also vulnerable, in this inner sanctum of masculinity, to self-criticism. The fears involved in being found out, finding an appropriate version of masculinity, navigating male social codes, or not knowing how to fit in after a lifetime of yearning: these are all played out. The very act of putting on the play, presenting his transition to the public, feels like an antidote to insistent self-questioning. There’s something awe-inspiring about being let in. By laying it out in such honesty, Kit gives us a terrific understanding of the process of self-realisation, carried out before our eyes.