From the outside, the Southwark Playhouse is a cul-de-sac behind a pub that should by rights be on the set of Lock, Stock . . . On the inside, though, it’s a trendy little venue under a railway arch – what isn’t, these days? – with chirpy staff operating an airline pricing system (book early, pay less). The sort of place where plays are not so much written as ‘devised’, and with an uncrowded, cheap-ish bar, to boot.

Presumption is devised and produced by Third Angel (not a hip-hop artist, it turns out). Beth (Lucy Ellinson) and Tom (Chris Thorpe) are “the generic thirtysomething couple of our time.” Beth was nearly killed this morning, and so is taking stock of her world: “It wasn’t my past that flashed before my eyes; it was his future.”

For Tom’s part, he wants to know “how ‘I love you’ turns into ‘Why do I love you?’ and then ‘Is it enough to love you?’” Presumption isn’t about poetic love. It’s about duration (or endurance, perhaps), the middle-term, stability, the fear – and cost – of breaking up, having to start again.

An empty, marked-up stage slowly fills with the props of their IKEA existence, as though every jointly purchased sofa is one more solid reason for the protagonists to be/remain together. And their conversations recur, at ever-increasing speeds (their voices turn middle-England when accelerated), while they consciously point out where to stand, which bits of set they’ve forgotten to bring on (they even put fresh waste-paper in the bin), and even errors in each other’s lines (a faux-faux-pas, or a pas-faux-pas, d’you think?).

The whole business is quick and clever and knowing – “If you go and get the cabinet it’ll be two days later.” – eye- and ear-catching throughout, the stagecraft prompting as many wry chuckles as the script does open, rueful laughter. Brilliant. And, in its shrugging, ‘hey ho’, English kind of way, the terrifying suburbanality underscored by the rumblings of the Jubilee line, more than a little discomfiting.

“That was everything I hope not to be in life,” Miss November stated emphatically over her Corona. I breathed a sigh of visceral relief, managing, just about, to disguise it as a belch.

n Southwark Playhouse, until Dec. 6. Tickets: 0844 847 1656 (