Greg Wise (Jake) and Oliver Gomm (Joey) in Kill Me Now
'Beautifully pitched': Greg Wise (Jake) and Oliver Gomm (Joey) in Kill Me Now
© Alex Brenner

We've barely settled into our seats at the Park Theatre when writer Brad Fraser hits us with the first excruciatingly awkward moment of Kill Me Now. Widower Jake Sturdy is giving his disabled son Joey a bath when the 17-year-old gets an erection - it's the first time that Jake has seen this happen and he's momentarily dumbstruck, unclear of how to deal with such a situation.

But then Joey breaks the tension, the theatre explodes into relieved laughter, and the play gets on its way. This happens again and again over the course of this beautifully pitched piece, Fraser taking us close to the edge of our comfort zones before rescuing the moment with a line that makes us laugh. Sex and disability, end of life planning, loneliness, emotional dependency - it's all in there, but presented with such a light touch, and so keen an instinct for storytelling that it all just washes over us.

The success of this technique depends very much on the sensitivity and fine comic timing of the cast. Greg Wise as Jake and Oliver Gomm as Joey both give astonishingly strong physical performances as they chart the course of a devastating role reversal in this parent-child relationship. It's to the credit of these able-bodied actors, and thanks too to movement director Fergus Early and voice and accent coast Yvonne Morley, that their physical efforts do not distract from their characters' emotional travails.

'I wouldn't be surprised if this production gets a West End transfer'

Jack McMullen as Joey's foul-mouthed pal Rowdy, Charlotte Harwood as Jake's spiky younger sister, Twyla, and Anna Wilson-Jones as his old flame Robyn provide an unlikely but highly effective support network. It's rare to see disability treated with such normality. Joey and Rowdy - whose mild learning difficulties make him hilariously tactless yet surprisingly perceptive - discuss sex in terms as obscene as you'd expect to hear from any other pair of teenaged boys. Jake has got into the habit of mollycoddling his son, dependent on being depended upon, but when it comes to Joey's relationship with Rowdy and Twyla, it's no holds barred.

Jack McMullen as Rowdy and Oliver Gomm as Joey
Jack McMullen as Rowdy and Oliver Gomm as Joey
© Alex Brenner

And there's no pussyfooting around any other issues either: when Jake can't get it up for Robyn at one of their weekly trysts (a clever device to keep the plot galloping forwards), the pair immediately talk about what they're going to do about it; when Twyla reaches the end of her tether as a result of her brother's declining health, she bellows at him that "it's time to stop being ill".

Not every relationship is so deftly handled. Rowdy's crush on Twyla is perfectly understandable, but it's a stretch to imagine that she would let the situation develop into a full-blown affair. Twyla's interactions with her brother and Robyn don't always ring true either - Harwood does her best with an underwritten character, but these are some of the play's least satisfying moments.

These small flaws notwithstanding, Kill Me Now represents a remarkable achievement for its whole creative team. Director Braham Murray keeps things simple and lets Fraser's clever, funny, heart-wrenching writing speak for itself, while Chris Davey's nuanced lighting design moves us neatly around Juliet Shillingford's uncluttered set. I wouldn't be surprised if this production gets a West End transfer - in fact, I really hope it does.

Kill Me Now continues at the Park Theatre until 29 March