There were a lot of noirs in contention for a place on my list. The Big Sleep, Criss Cross, The Big Heat, The Killers - all do one or two aspects of the genre exceptionally well and any would have been worthy of inclusion. But none of them are nearly as well-rounded a film as Double Indemnity. It's got everything: a genuine hard-boiled script, seductive femme fatale, a dleuded straight-guy sap, pervading sense of death and existential fear - all watched over by one of cinema's great directors, Billy Wilder. It's not just a defining noir moment, but a superb film - period.

Firstly, there's the cast: Fred MacMurray and Edward G. Robinson both playing against type - the former usually playing the good guy in lightweight comedies, the later a nard-as-nails gangster thanks to the success of Little Caesar. MacMurray's comedy expereince certainly pays off in the dialogue-heavy repartee his Walter Neff shares with Barbara Stanwyck's Phyllis Dietrichson. He's enamoured with the leggy blonde the moment he sets eyes on her, but all she see is a willing dupe. Getting their adulterous relationship past the censors was one of the reasons an adaptatin of James M. Cain's novel had languished in development hell for over a decade.

Meanwhile, it's Robinson's turn to play it straight as Neff's manager with the "little man" inside that gives him all his hunches on the dogs trying to run a scam. The casting still works beautifully today - Robinson is his usual pocket-rocket self, creating a character much larger than his diminutive stature, which must have been a real treat in 1944 when actors and actresses were contracted to the studios and generally wound up playing the same kind of roles over and over.

Walter and Phyllis' plan is deceptively simple: get her husband to sign a life insurance contract with a double indemnity clause (double the payout in cases of accidental death), murder him, collect the monet and drive off into the sunset. Walter, thinking he can beat the system because of his eleven years as an insurance salesmen, thinks he's planned it perfectly ("One night you get to thinking about how you could crook the house yourself, and do it smart.") The ironic thing is, he's seen it all before and knows full well that no one gets away with it, especially not while Robinson's Barton Keyes is on the prowl. This is where the film's awareness of death is made apparent. We know from the opeing scenes that Neff fails - or at least that something goes horribly wrong - and it's the spectre of death approaching that compels Neff to record his confession on Keyes' Dictaphone, allowing the story to be unveiled in a series of flashbacks.

Billy Wilder could turn his hand to almost any genre with success because of his unwavering adherence to writing and story. In the case of Double Indemnity, he didn't simply take a ready-made noir toolkit and try to hang a story on it, but rather utilised what would become many of noir's chief characteristics to add drama and tension to what was already a riverting story. Though he might have become known for his somewhat conservative style. Wilder's work on Double Indemnity helped to establish certain filmic techniques as particularly noir-ish conventions, such as the use of venetian blinds for shadows and voice-over narration; the later born out of necessity as a way of getting around the Hays Code, since we're to assume by Walter's confessional, resentful tone that he has come to regret his actions: "How could I have known that murder could sometimes smell like honeysuckle?"

The film originally ended with Neff being executed in the gas chamber, but this was excised in favour of the existing, much better, ending. It's enough that we know Walter's eagerness to cross the line and commit murder for sex and money will be suitably punished. What we really want to see is that final moment that Keyes shares with his friend; the compassion under the brusque exterior. It's this kind of dichotomy - the best and worst of humanity - that lies at the heart of the very best noirs, amongst which Double Indemnity most certainly has a place.