There are movies so bad that they transcend awfulness. Ed Wood's Plan 9 from Outer Space and Glen or Glenda? perhaps, or Troll 2. And then there is William and Kate: The Movie.
Coming to a DVD outlet near you shortly. So bad it's awful, toe-curlingly, teeth-furringly, pillow-bitingly ghastly. You begin to wonder what the happy young couple have done to deserve this. It will probably be a smash.
Perhaps the PR handout gives it away: "Shot entirely in Los Angeles and inspired by true events." That might account for the mountains in the backdrop to a pheasant shoot in Gloucestershire, buses driving on the right in London, the Middletons' modern house transformed into a Californian Tudor mansion and the famous dragon boat race training that Kate Middleton once undertook on the Thames at Chiswick being transposed to the High Sierra.
The film has sparked a worldwide media frenzy, according to its promoters. This is the Wedding of the Year as imagined in Wichita or Wyoming, with dialogue so authentic it follows you round the room. As in all the best plays, they tell each other things they must already know. "I say, Wills," says Prince Harry. "I am not the heir. I am just the spare."
"You do realise this is the 21st century?" Kate expostulates to her etiquette coach. "In your world, perhaps, but not in his," said coach replies portentously, and a million heads will nod knowingly, from Houston to Hawaii.
Monarchists abroad may be shocked when William informs his intended that half the country loves his family and the other half thinks they are irrelevant throwbacks – a little bit of social comment there – but they will soon be back on track when he adds reassuringly: "My mother was one of the people. She tried to change the monarchy."
Kate replies: "We'll still be us. Nothing will come between us." At which point some in the audience at the film's preview unaccountably began to titter.
Prince William – aka "the Royal Beau" – is played by young New Zealander Nico Evers-Swindell, whose acting varies from plain wooden to teak-like, which may not be so far from the original, but is somehow less engaging. Who could blame him, saddled with lines such as: "I am sorry … I just need some space." And air, by the looks of it.Middleton – whom everyone in the movie, including Prince Charles, calls Kate, unlike in real life where she's known to friends and family as Catherine –is played by Camilla Luddington, an actor whose last part was as a teenage drink-driver in CSI. Luddington was apparently brought up in Berkshire, like her alter-ego, but, if so, she's clearly spent too long in the US because her accent is more Berkeley than Bucklebury. Ben Cross, who once strode across Chariots of Fire, gives us his Prince Charles and he has certainly got the cufflink-fiddling off to a T.
It is the little things that jar. Like the German spy in the old war movie who gives himself away when he doesn't know who won the Cup final in 1938, or the ex-boyfriend who announces he's going to "the college of law at Oxford", or the reference to the happy couple's alma mater as St Andrew's College: apparently it's a school, too.
Perhaps the Scottish university had an inkling of what the film would be like and sensibly did not let the cast and crew anywhere near: there are only aerial shots of the town, interspersed curiously with an overhead view of Oxford. At ground level the university looks suspiciously more like an Ivy League campus.
The tabloids and paparazzi get it in the neck for hounding Middleton, which is odd coming from a film which makes a virtue of its intrusiveness.
Fortunately the Queen does not appear – perhaps Helen Mirren was too expensive for the £3m budget – probably saving her from telling her granddaughter-in-law-elect to: "Get with the programme, sister."
As the happy couple's love entwines against a sunset as livid orange as any in Gone with the Wind, there will not be a dry eye in the house. But possibly not for the reasons the makers suppose.