I went to see James Corden in his new film 'One Chance'. Cheeky Chappy plays Paul Potts, the goofball nobody from nowhere who won the first-ever series of 'Britain's Got Talent' in 2007, and gave a performance at the Royal Variety for Her Majesty the Queen. Against all odds do losers like Paul achieve greatness, is the message. The movie lacks the style of 'Billy Elliot', to which it has been compared. Nor does it do much for Julie Walters, usually perfectly-cast in everything, whose role as Potts's doting mother deserves more screen-time. With the big guns behind it - Weinstein, Cowell - it is no-expense-spared. The location work in Venice is sublime. It features shameless product-placement: Carphone Warehouse, Boots the Chemist. It has the requisite happy if so-what ending. For the real Paul Potts, despite having shifted five million copies of his three albums, the debut also called 'One Chance', has not metamorphosed into the Pavarotti-style opera singer he yearned to be. He's a good enough light tenor concert performer now and again. A recording artist, primarily, with  the requisite charisn'tma to be just that.

I made myself take the night to digest. I'm still a bit sad about it. You might think that a former hack would be immune to a little truth-bending. Granted, the disclaimer is clearly displayed before the film starts: that the feature is based on a true story. In which case, why call the guy Paul Potts?

The first thing that grated on me, a Welshwoman, was Corden's lack of Welshness. It was pathetic. The bugger lives in Port Talbort. His pronunciation of his town annoyed me too: we say TALbot, not TALLbot. The real Paul spent his childhood in Bristol before moving to Wales, and speaks in an accent best described as Bristolian Welsh.

Potts the Real has a degree in Humanities, and once worked as a Bristol City councillor. Corden's Potts was a bullied academic failure with no future beyond that of salesman in the local mobile phone shop and a brief stint in the steelworks. The distortions thereafter come fast and thick, not least the beam-me-up depiction of his wedding night, when Paul confesses to Julz (in real life Julie-Ann,  played by Alexandra Roach) that he has 'never done this before.' 'I've had thousands,' his bride deadpans. The real Paul had his share of girlfriends too. To portray him as a fat, fumbling virgin, on top of his other loserliness, was a stretch too far.

The moral of the Paul Potts story is this, isn't it: that without the magic wand of Simon Cowell, Potts might still be toiling in the phone shop or shovelling slag. Like Susan Boyle, he dreamed a dream. He made it over the rainbow: one of the few I-want-this-sooo-muchers who did. What happens to the losers beyond the money-spinning tours? Who cares. Cowell can't do. He is reborn as the Wizard of Oz, reinforcing his own self-madeness. Dishing out brains and hearts, and courage, and teeth. Winging Dorothy Gale back to Kansas. Making Emperor's New Clothes.