Tree, Old Vic

There is a tree on stage. Not a real tree but a full-size fake one (made by Take 1 Scenic Services) that reaches the ceiling, with lots of branches and leaves. As the audience enters the Old Vic auditorium for this in-the-round production (first seen at Manchester Royal Exchange in 2013) they have to cross the stage, where performers Daniel Kitson and Tim Key are laying tape into various shapes on the floor, an act that will be explained much later in the evening.

To begin proceedings, Kitson (pictured below right), who also wrote the show, climbs into the tree, where he spends the entire 90 minutes scampering around from branch to branch. Key's character (neither is named) enters, rushing and flushed. He's late for an assignation under the tree and as the evening unfolds the two men tell each other why they are here. "What are doing up a tree?" Key (pictured below left) asks. "That sounds like a straightforward question..." Kitson begins, but we know the answer will be anything but.

We learn that Key's character (aka "the pillock" because he's always getting things wrong including what time of day it is, hence his lateness) is here to see a woman he has recently met for the first time in 10 years – and they are to have a picnic in the shade of the tree. Kitson's character, meanwhile, tells us he has lived in the tree for nine years in an attempt to stop the council from cutting it down – as workmen have, we eventually learn, the others in the road, their stumps outlined by the sticky tape on the floor.

The two men share their histories, partly as conversation, partly as storytelling and, as ever with a Daniel Kitson work, with acute attention to detail and human observation, with callbacks, repetition and comic asides often there for no other purpose than to be funny rather than to move the narrative along.

We're more used to seeing Kitson deliver monologues and there's a real pleasure in seeing him flesh out a story playing against another actor, but there's little drama as such, although he creates a lot of funny business with the orange bucket by which, he tells the pillock, his friends deliver his food and reading material. His toilet habits -– "always the first question people ask" – are taken care of not in the bucket but "number one in a bottle, number two in a bag". When Key's character reacts with disgust, Kitson cries in response: "I triple-bag it - I'm not an animal!"

The themes that Kitson returns to time and again in his work are here - love, longing, the life unlived - but so also is a playfulness with the audience, keeping us guessing throughout where these stories are going. Kitson and Key deliver engagingly naturalistic performances and, while the evening flags slightly, Kitson delivers not one but two reveals (one for each character) to make for a very pleasing payoff.

• Tree is at the Old Vic Theatre until 31 January