A play about an ex-cellist with cancer and the relationship she has with her social worker? Um, I think I’m doing something else that evening…

But wait, come back, because you haven’t met Hester yet. She really is quite something. Shunning chemotherapy for Rioja and her beloved Brahms for endless TV boxsets, Hester (Bridget Forsyth) is a woman ageing disgracefully. Except that ‘ageing disgracefully’ is in itself a cliché, and one of many tropes that Zoe Mills’s smart, tight, funny two-hander artfully dissects.

The portrayal of illness here is refreshingly unsentimental, with the patient in question neither howling at the wind nor virtuously handing out feelgood platitudes from her deathbed. Hester, we assume, is carrying on much as she always has – gravely ill, but still annoyed with herself for finishing the cream crackers. Mills is terrific as the troubled, Twitter-happy Sara, a character who again isn’t necessarily what she seems. The fact that we’re seeing a real life mother and daughter onstage shouldn’t perhaps matter, but it does add another layer of poignancy – at the curtain call, you could be forgiven for finally allowing yourself a ‘something in your eye’ moment.

It has the beats of a sitcom, an artform at which Forsyth is obviously a master. But as in all good sitcoms, the edges between darkness and light are frequently blurred; the humour isn’t there simply to sugar the medicine – it’s an essential part of the medicine. Hester is foul-mouthed, but Mills resists the temptation to go for cheap ‘Ha ha, old lady swears a lot’ laughs – Hester’s profanities feel natural, as if she’s spoken that way her entire life. There are no overwritten zingers – just dialogue that feels real. At one point Hester chides Sara for talking like she’s in Thelma and Louise.

It’s an ambitious work too, making good use of  crazy-paved video screens, growling soundscapes and a serenely revolving stage. The cello music is also used well, driving the drama rather than merely garnishing it.

It’s a play about, among other things, social media – particularly the way we attempt to shape our identities but also surrender ourselves to being shaped by others. It’s also about two women drinking wine. I recommend it anyway.

Killing Time is at the Park Theatre in Finsbury Park until 4 March