They say that behind every great man is a great woman - or two great women if you are the poet Dylan Thomas. John Maybury’s film is different from the usual biopic because it’s really the love story of the two great women, Vera Phillips (Keira Knightley) and Caitlin MacNamara (Sienna Miller), behind the great man. And I don’t mean that kind of female love. No, this is the kind of female love that dare not go all the way - it’s the intimate, tender, mutually supportive kind of platonic love that is founded on the quicksands of friendship.

Maybury may claim that this is not a film about Dylan Thomas, but you wouldn’t be watching these characters if they weren’t connected to him. A film featuring a glamorous-looking Knightley and Miller, though, is going to generate a lot of media heat, if not box-office revenue. And all the leads in The Edge of Love look terrific - even Dylan Thomas (played by the handsome Matthew Rhys), who in reality was almost as ugly as Dr Johnson.

This glam-looking cast find themselves in London during the Blitz. Maybury evokes a dark, dingy world of bedsits, smoky pubs and crowded Underground stations. It’s there that we first meet Vera, singing, and witness the handsome Captain William Killick (Cillian Murphy) come under her spell. Later, Vera runs into her first love, Dylan, who immediately wants to rekindle their old flame. They are clearly interested in each other, but up pops Dylan’s wife, Caitlin, who warns Vera to back off. Still, it isn’t long before the two rivals become the best of friends.

Although the film has four love stories, none of them is strong enough to hold our interest. Maybury depends too much on the beauty of his two leading ladies to captivate us, and not their characters. I, for one, don’t share his love of the Knightley look. She has such a cold and conceited screen persona, with that spooky Bambi-meets-Tony Blair smile. Miller, on the other hand, manages to look great and still be likeable. Neither actress, however, comes up with the outstanding performance the film desperately needs. It wants to be a big emotional story about love and loss and friendship, yet you leave the cinema feeling nothing in particular. It never strikes a chord because there’s nobody on the screen we can care about.

Dylan Thomas emerges as a loathsome human being: infantile, spoilt, a liar who will destroy a man - whose money he is happy to squander - to get what he wants. (And he actually says things like: “I sleep with women because I’m a poet.”) Caitlin is meant to be a boho girl and free spirit, which is a posh way of saying she’s a drunk who is promiscuous. The world is at war, Britain is struggling for survival and here are a bunch of young people happy to get drunk, sleep around and mess up each other’s lives.

The most disappointing thing about The Edge of Love is the screenplay, written by the once promising playwright Sharman Macdonald, who happens to be Knightley’s mum. Here was a great opportunity to create some real, fascinating female characters with rich inner lives, but it doesn’t happen. Vera is a singer, but nobody ever talks to her about singing. Does she want to make records or have a career? At one point, Caitlin talks about her talent being submerged by Dylan’s, but what exactly that talent is remains a mystery, because nobody is interested in what these women have to say: about poetry, the war, politics, singing or anything other than men and babies.

I suspect that Knightley and Miller off screen would generate more interest than on screen. There’s no dramatic spark between them and the dialogue is insipid. When they meet, Caitlin, who knows about her husband’s past with Vera, says to her: “I might like you - and, then again, I might not.” Vera looks at her and says: “I’ll await your decision, shall I?” It’s hardly Bette Davis and Joan Crawford in action.

Why is it that in modern films and television dramas, female friendship can be expressed only by women acting like stupid teenagers? We see Vera and Caitlin cooing, hugging, giggling, screeching and sharing a bath together - but they never share an idea.

The Edge of Love is ultimately about nothing in particular, not even female friendships. It has the pretty frocks of Atonement, and the love-interrupted-by-war theme, with the female solidarity of Sex and the City. It is all surface and no substance.

15, 110 mins

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