Southwark Fair, NT Cottesloe, London

Enter Puck, followed closely by Patrick...
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This is the South Bank holding the mirror up to the South Bank. Outside the National, the grey stone balustrades stretch along the Thames, with strings of lights looping into the distance, past designer eateries.

And inside the Cottesloe, those selfsame sights are reassembled on stage. Samuel Adamson's new, pain-flecked, metrosexual rom-com - directed by Nicholas Hytner - misses the opportunity of having its characters teasingly hang out at the NT or the Globe. That is slightly surprising since they talk about theatrics and quote chunks of Shakespeare. Still, they all keep crossing paths in the vicinity, wandering between Tooley Street and City Hall.

Rory Kinnear's Simon is a laughable loser yet also a sympathetic singleton having a bad day. He is bunking off work for a hopefully romantic reunion, as he explains to his grandmotherly neighbour, a cranky bit-part actress called May (Margaret Tyzack). He has a lunch date with Patrick, his never-forgotten first love, to whom he lost his virginity, aged 14, on a holiday drama course - to be precise, in the toilets between Acts III and IV of A Midsummer Night's Dream in which Simon was, we later glean, a lousy Puck.

It's only breakfast time and, being a nervously apologetic type in a rude society, Simon is already taking flak from a surly waiter, Michael Legge's Aurek, and a crushingly cool busker. Worse, it turns out Con O'Neill's seedy, sexoholic Patrick - who was a 20-year-old director on that summer course - barely remembers Simon. He has gallingly confused him with his ex-Lysander and is soon leering at Aurek. Simon is then followed and punched by Patrick's fuming rock-chick wife, Toni, who is being pursued, in turn, by the busker.

In the second half, Adamson doubles back, replaying the day but from different perspectives, showing what a hard time the others were having too, behind and between the previous scenes. The dialogue is sporadically hilarious, especially when Simon gets snarky. Both Kinnear and O'Neill are compulsive viewing, shifting from terrifically awkward small talk to seriously shaken distress. One might also see this as an interesting coupling with Bennett's The History Boys, Hytner's last NT production. Both raise questions about paedophilia, degrees of culpability and of lasting damage caused (or not) - issues also grappled with in David Harrower's Blackbird, currently in the West End.

But really Southwark Fair feels like superficial fare, lightweight, whimsical, drifting towards schmaltz. A somewhat drab and cluttered set - including an architect's model tower block - doesn't help, and some cast members hadn't managed to make their characters 3-D when I saw this production's final preview. Adamson has done some fine adaptations of late - including Pillars of the Community - but there's a present shortage of really good new plays and this is certainly disappointing in a peculiarly thin season at the National.

Booking to 5 April, 020 7452 3000