The Ha'penny Bridge at The Point, Dublin

There are at least three good reasons to approach Alastair McGuckian's new musical The Ha'penny Bridge with some trepidation. A wealthy businessman putting money into a lavish production for which he has written the book, lyrics and music smacks of a vanity project. The cavernous Point is a terrible venue for any kind of theatrical production. And the advertising blurb - "A love torn apart in a country divided" - s uggests yet another lurve-across-the- barricades plotline.

None of these fears turns out to be entirely ungrounded. There is a degree of self-indulgence in The Ha'penny Bridge, with a running time of two-and-a-half hours plus interval, and at least three numbers that any objective producer would have culled. The vast spaces of the Point make any kind of subtlety - always at a premium in musicals anyway - impossible. And the plot does turn on the doomed love affair between a Dublin woman and an English veteran of the Somme during the Irish civil war. But The Ha'penny Bridge is much odder and rather more endearing than all of this might imply.

In interviews, Alastair McGuckian has revealed that he had trouble thinking up a name for his show. It is easy to see why: Juno and The Paycock was already taken. For The Ha'penny Bridge turns out to be not so much an account of civil-war Dublin as an account of the literature of civil-war Dublin, with a few bits culled from other sources, all set to a pastiche of 20th-century American musicals. An alternative title, if it, too, were not already taken, would be The Thieving Magpie.

Ninety per cent of the book is straight from Juno. Annalene Beechey's Molly is Mary Boyle, the intelligent working-class girl who wants to better herself. Flo McSweeney's Anna is the stout-hearted Juno. John Conroy's Peadar is the blustering ne'er-do-well Captain Boyle and Mark Lambert's Whippet is Joxer Daly. Karl Harpur's Sean is Tancred and Eileen Reid's Maggie is Mrs Tancred complete with "where were you?" lament. The seducer, Stephen Ashfield's George, is slightly different in that he is both English and decent, but the key elements of the plot - the diehards, the murder, the Captain's attempts to avoid an offer of work, the unexpected windfall, the pregnancy - are all booty from a raid on O'Casey's cupboard.

Of the other 10 per cent, half is from Liam O'Flaherty's The Informer (O'Flaherty even appears to make a speech), a third is from Brian Friel's Translations (English boy meets Irish girl - cue a song about the colourful Irish language) and though the rest is of McGuckian's own invention, it is pure hokum. Put all this together with a series of musical incursions on everything from Oklahoma to Cabaret and you get a piece of work that might have been produced by a man locked in a room for a decade with a few Irish classics on the shelf and a series of MGM musicals playing on a constant loop.

It's this off-the-wall conjunction, though, that saves The Ha'penny Bridge from dreariness. It acquires at times an almost surreal quality, best summed up in Bill Deamer's seriously strange choreography for the 18-strong dance company. Deamer picks up on the prevailing mood of anomalous juxtaposition, and creates a dizzy cocktail of Riverdance, Bob Fosse, classical ballet and the Moulin Rouge that is far too compellingly peculiar for anyone to be able to say whether it's any good.

All of these anarchic collisions would usually create a mess, but what makes The Ha'penny Bridge so idiosyncratic is the way its quixotic charm is bolstered by a rigorous professionalism. The big roles, especially McSweeny's, Beechey's and Ashfield's, are superbly sung. Conroy's somewhat zany presence as a camp Captain Boyle is sustained by a real pro's ability to occupy the stage. A touch of class is added by having a proper orchestra, under the constantly inventive direction of Gearóid Grant. Cathal McCabe likewise orchestrates the action with impressive fluency on Patrick Murray's clever and sometimes striking sets. The sheer scale of the whole thing - which has quickly overtaken The Wiremen as the most lavish Irish musical ever - gives it an energy that drives it forward in spite of the absurdities of the plot.

And McGuckian, at least, has something to say. The Ha'penny Bridge is a strained parable on contemporary Northern Ireland, and its attack on violence and plea for social justice lead to an unhappy ending that has the guts to swerve away from sentimentality. It took a thick skin to mount a show as eccentric as this one and it would take a hard heart not to grant this Don Quixote a degree of bemused respect. Fintan O'Toole

Runs until 25th June