His Girl Friday, National Theatre Olivier London

"I'm trying to find the way to death row," bleats the confused, doddery cleric in a running gag in this new show at the National. You'd have thought that the swiftest route to that spot, for a writer, would be to participate in the kind of thing that is being attempted in this piece. Two legendary and near-perfect comedies have been synthesised in the hope of coming up with a third smash. US dramatist John Guare could now be ordering his last meal, convicted of gross presumption. Instead, we are delighted to issue a reprieve and a public apology for doubting him. Temerity evidently pays, and so will this show which, despite its flaws, looks set to become the theatrical hit of the summer.

The playwright has taken His Girl Friday, Howard Hawks's classic movie comedy, which was released in 1940, and conflated it with The Front Page, the 1928 Hecht and MacArthur play on which it was based. Both those pieces are hilarious love-hate letters to the inky trade of journalism, in which the two authors had misspent their youth. But the film adds sex to the brew by a simple switch of gender. It's not just his most brilliant reporter but his ex-wife, Hildy Johnson (Rosalind Russell) whom the unstoppable editor, Walter Burns (Cary Grant) must prevent from leaving the paper and from remarrying.

The movie shifted around various locations. With most admirable skill, Guare adapts the scenario so that, like The Front Page, it all takes place on the one set: the press room of the Criminal Courts building in Chicago. This has one or two questionable effects on the narrative sequence. Hawks was careful to establish at the outset the comic tension in the relationship between Hildy (who thinks she wants a life of quiet domesticity with her insurance salesman fiancé) and Walter (who knows that she's a newshound to the bone and who will use any dirty trick to get her back). He's characteristically opportunistic in seizing as pure bait the story of the cop-killer who is about to hang wrongfully because it's seen as a vote-winner by the corrupt mayor and sheriff. In this new play, though, Alex Jennings's editor has already established his credentials as a somewhat less ambiguous crusader for justice by the time Zoë Wanamaker's Hildy makes her delayed entry into the press room. Given the unity-of-place convention, this ordering was probably inevitable, but it gets the priorities the wrong way round and it blunts the point that, though their goals may be different, the methods of the press and the politicians are comparably outrageous.

Jennings and Wanamaker are a knock-out combination. He's wonderful at projecting Walter's domineering charm and serene unscrupulousness; she's terrific as she conveys the alternating excitement and dismay of a feisty dame who is coming to realise that she's genetically doomed to serve a life sentence in the trade she half-despises. Walter recalls the remark about Fred and Ginger: "She gave him sex; he gave her class". But that's unnecessarily invidious here, since in chemistry of the Jennings/Wanamaker partnership, each gives the other both. One of Guare's most inspired original touches is the literally-shotgun remarriage at the end. "You can forget the 'obey'," objects Hildy. "That's OK - just keep typing," replies Walter who has his bride bashing out a scoop, at gunpoint, even during the wedding ceremony.

Guare has relocated the proceedings to the brink of war in 1939. There are now some uneasy and rather dutiful interpolations. The boring fiancé (attractively played by Richard Lintern) now reveals obnoxious political opinions, derived from his mother, about Hitler being a regular guy who just wants living-room for his country. Highly amusing, though, that this Walter intends to become a campaigning non-isolationist, given that all his instincts are to keep Germany's invasion of Poland off the front page in favour of the local scoop.

Jack O'Brien's production needs a touch more comic topspin in the first half, but after the interval, as the farce speeds up, it achieves take-off into bliss, with some wildly-funny interventions from the prospective mother-in-law (Margaret Tyzack, superb as a befurred battleaxe with a militant hatred of female authors). The trade-off here between stage and screen is embodied in Bob Crowley's black-and-white design. It's gently suggested that these are actors being filmed on a soundstage in LA. Like the adaptation, it's a clever hybrid - resulting in a clear hit.

To 22 Nov (020-7452 3000)