The Bush Theatre has turned blue. The stage, the walls, the block-furniture, the seating – everything is sunk in blue, with white clouds scattered everywhere. But although Lucy Osborne’s set is undeniably striking, it is also misleading. The excellent new play by Nick Payne, winner of the George Devine Award for Most Promising Playwright 2009, might revolve around a suicidal teenage girl, but blue it ain’t. If There Is I Haven’t Found it Yet is serious in intent and emotional in places - yes, but also much funnier than most all-out comedies you’ll see and much, much funnier than the predominantly earnest new plays we’ve come to expect.

Osborne’s distinctive set also suggests a surreal, floating piece, but the strength of Payne’s confident, modern play, is its accessibility and believability. Payne has picked a familiar but neglected character for his central role – an overweight teenage girl – and plonked her in a local, real situation amongst slightly nuts but recognisable characters. It is a witty and sharply observed piece – and whilst Payne is a comic writer first, he also uses his play to suggest that society’s obsession with the bigger picture (global warming, anyone?) is threatening to overshadow the present, as well as the people we share that present with. Perhaps this idea of the ‘big’ overtaking the ‘little’ is what Osborne is hinting at with her set, but it doesn’t capture the forthright tone of this piece and lends it an over edgy feel, which the performers initially have to work against.

Thankfully, the opening scenes are too energetic, buzzing and fizzing, to be restricted by the set for too long. The piece begins with Anna - played by an exceptionally open and vulnerable Ailish O’Connor – lounging about at home, Doritos in hand, having just been suspended from school following a punch up on the netball court. But it isn’t just Anna who has been getting into scrapes, and her sulky idyll is torn apart by the arrival of uncle Terry, who has problems of his own and has retreated to his brother’s house for food, rest and recuperation.

It isn’t hard to guess where the play goes next. The two young-uns - more than a decade apart but damn near equals in mental age and maturity – talk, tease, bicker and bond. Anna’s parents are conspicuous in their absence (particularly her father, whose consuming concerns about global warming have left him with little warmth for his daughter) and the wayward but big-hearted Terry plugs the parent gap with ease and grace.

It is the development of this central relationship that is the real joy here. Theirs is an unusual dynamic – characters this age don’t take centre stage much - but rather than mine this situation for ‘profound’ gems, Payne lets his carefully selected scenes and spot-on banter do the talking. There is an excellent scene – unforgettable in its own unassuming way – when Terry gives Anna sex advice, whilst she helps him with the finer details of preparing a pie. The scene is written with a light touch – it feels close and small – but it also says a lot about a teenager’s need to be needed and the lessons these two have to teach each other. It is warm, funny and honest. The best line is worth quoting and comes when Terry advises Anna on her upcoming first-date: ‘Watch your back – quite literally, Anna.’

If O’Connor’s soft, gentle teenager Anna is the heart of this play then Rafe Spall’s Terry is its sparkle. Spall is a ridiculously charming comic actor with a spreading, easy grin that nullifies his character’s more thoughtless, flippant remarks. It is rare to see an audience warm so fast and so surely to an actor, but Spall has the blue-seated spectators on his side from the off. O’Connor and Spall (helped along by Josie Rourke’s smart and pacey directing) mine the very best from Payne’s writing and their scenes glitter with charm and easy affection.

The play veers slightly off track when Terry flees to the coast, leaving Anna and her parents to fend for themselves. Spall brings such a tangible energy to this piece – and Anna is so openly wrapped up in him – that everything droops a little with his exit. The other problem is that Anna’s parents – who, up until now, have been peripheral figures played largely for laughs – take on much bigger roles. They don’t feel ready: their characters are a touch overplayed and it is a stretch to suddenly take them seriously.

Michael Begley in particular, pushes his character’s comedy too far. Playing Anna’s father, an academic decked out in tweed and with a permanent pinched nose, his role is already a natural figure of fun. It is all there in the writing and there’s no need for the actor to layer too much on top. Unfortunately, Begley can’t resist amping up his role and although this results in some excellent isolated moments (the best bit being near the play’s opening, when George hears about his daughter’s scuffle at school and corkscrews to the floor, knees dropping and wailing ‘suspension!’ in despair) it also leaves him with little to fall back on, as the play darkens in tone.

Though this piece stutters slightly in the second half, O’Connor’s Anna gives off such a strong, emotional pull that she holds the shakier scenes in place and lights up the stronger ones. One scene late on is heart-breaking in its simplicity: Anna takes a bath, alone and silent on a raised and isolated platform. She sinks into the water, weeping - hugging, hating and pawing at herself - somehow trying to disappear this body she has found herself with. It is scene that stands alone – but is also one that cuts to the heart of this honest and thoughtful play. It reminds us that, while adults might be preoccupied with the bigger picture, for teenagers the small details are the bigger picture. If parents fail to recognise the importance of these small details in their children’s everyday lives, they fail to recognise their children altogether.

Till 21 November 2009