There is only one Christmas film and that film is It's a Wonderful Life. There are pretenders to the title and certainly A Christmas Carol is a claimant: its ghostly Victoriana, plump turkeys and 'God bless us, every one' are virtually a blueprint for the Christmas card industry.
But Dickens's tale is the story of a bad man finding redemption. Frank Capra's Christmas masterpiece is the story of a good man, nearly crushed by his own decency, redeemed by the love and goodwill of the people he has done so much for.
It's a Wonderful Life is the story of a man's stifled dreams. Throughout his life, circumstance has dictated that George Bailey must never leave Bedford Falls, the small-town American idyll, where he was born.
Bailey, as portrayed by James Stewart, is an Everyman with everyday problems: raising and providing for a family, looking on as other people fulfil their dreams, while his own remain unrealised.
But he has bigger problems than this: his own sense of responsibility has made him the rallying-point of opposition to the "richest and meanest man in town" - Henry F Potter, slum landlord and majority shareholder in the Building and Loan, who has made it his business, literally, to destroy the lives of the local working poor. When George intervenes on behalf of the little people, he makes an enemy for life.
Lionel Barrymore's Potter, Montgomery Burns with a year-round hangover, is so compellingly malevolent that he made the film the subject of an FBI investigation.
On May 26, 1947, the FBI issued a memo stating: "With regard to the picture It's a Wonderful Life: the film represented rather obvious attempts to discredit bankers by casting Lionel Barrymore as a 'Scrooge-type', so that he would be the most hated man in the picture. This, according to these sources, is a common trick used by Communists."
This does tend to rather misread the situation, given that this is a film where the main character is a bank manager, not a traditional occupation for your average-Joe hero.
In fact, it is not white-collar crime to which Potter resorts, but a good old fashioned swipe. George is on his way to the bank to deposit $8,000, but stops to read Potter some newspaper headlines.
An angry Potter snatches away the paper, accidentally nabbing the $8,000 with it. He notices immediately, but keeps quiet about it.
George doesn't spot a thing and goes about his business, whistling merrily, leading one to conclude he's not quite the safe pair of banking hands the townspeople think he is.
Panic ensues when George realises that the money has gone and, in desperation, he goes cap-in-hand to the only man in town who can save him: Henry F Potter.
Potter, true to form, uses the occasion to gloat and then swears out a warrant for his arrest. George, desperate, heads to the nearest bar, slams his car into a tree and staggers to a bridge, where he intends to throw himself into a river and drown. So far, so Christmassy.
But there is already someone drowning in the river and, when George rescues him, he reveals himself to be Clarence, an angel hoping to get his wings.
George, quite reasonably, doesn't believe him and bitterly wishes he had never been born, a bad choice in front of an angel, as he's soon off on a whistle-stop tour of the town without him in it.
And, wouldn't you know it, it turns out that everybody's lives are the better for knowing George Bailey.
What makes this such a Christmassy film? Well, one reason could be that it started life as a Christmas card.
Originally based on a short story by Phillip Van Doren Stern, called The Greatest Gift, Stern found he was unable to get a publisher, so he turned it into a Christmas card and mailed 200 copies of it to family and friends.
Director Frank Capra read it and immediately saw its potential. In a sense, it is another version of A Christmas Carol. Both feature a man revisiting his life and potential death with the help of supernatural agents, culminating in a joyous epiphany and a renewed sense of the value of his life.
In a sense, Dickens's tale shows us the story if Potter had been visited by a guardian angel. George Bailey is very much in the Bob Cratchett mould: an ordinary man, straightened by circumstances and trying to do the best for his family.
The underlying theme of the film, its Christmas message, is that a person's true worth is not measured out in last-minute tat bought from a petrol station en route to a Christmas party, nor even in a carefully wrapped Xbox lying tantalising beneath the tree. It's in the fact that George is reunited in the love of his family and that of his community.
When his brother toasts him as "the richest man in town", this is palpably untrue; George is bankrupt. But he has the knowledge that he is loved and valued and that should be the true message at Christmas.
That warmth, that decency is the lasting legacy of It's a Wonderful Life: THE Christmas film.