There's an undeniable feeling of excitement sitting in the Theatre Royal Haymarket stalls when the lights come up and you're confronted with Maggie Smith on the stage, joined within moments by Judi Dench.

These two grand Dames of British theatre have never appeared together on the West End stage so it's a momentous occasion indeed. And the ladies are, indeed, worth the wait: breathtaking to behold singly and doubly so together. Two 'women of a certain age'- not quite middle age and certainly not old age, as author David Hare writes in the programme notes; rather a point at which they have "a long past behind them, but the expectation of a considerable future in front of them" - who have come into that age with all the grace and power and beauty of lionesses.

Smith and Dench bring those qualities and more to their parts in this world premiere of Hare's two-hander. Smith is retired museum curator and free-spirit Madeleine Palmer, at home in her Isle of Wight flat (designer William Dudley's bohemian enclave with tall windows, throw cushions and flaking-paint ceiling, all beautifully lit by Hugh Vanstone in hues of seaside sunsets, sunrises and boardwalk neon) when Dench's Frances Beale, the pulp novelist ex-wife of her ex-lover, turns up unexpectedly.

Frances is seeking 'closure', "some sort of end to the pain" of her husband Martin's betrayal and eventual family desertion into the arms of yet another (younger) woman. But Madeleine, still smarting from her own decision to settle for less and "be defined by my need for this man", is in no mood to offer either solace or apology.

David Hare is a writer of great intellect and sensitivity. This latest play of his - which he admits, he found tougher to write than any other he can remember - is rich in amusing lines, thought-provoking ideas and full-bodied rants (Americans, be warned), given an elegant treatment at the hands of director Howard Davies.

And yet despite Hare and Davies, despite Smith and Dench, despite this inredible assemblage of talent, a subversive thought creeps into my mind half-way through Act One, growing and growing through Act Two until it cannot be denied: this isn't very interesting. The problem is, nothing happens. The women talk a lot - and too much about the awful Martin, with lots of he-said's and I-said's - but never really get anywhere.

Certainly, neither woman seems terribly stretched by the material. I found myself repeatedly wondering how Dench would play Madeleine and what Smith's Frances would be like. Perhaps a bit of nightly role-swapping - as Mark Rylance and Mark Rudko did to scintillating effect in Sam Shepard's True West at the Donmar in 1994 - could help to up the ante. Not that any help's needed in selling more tickets to this sell-out event.

- Terri Paddock