It is one of the headline acts of the BBC's festive television schedule, enjoying a prime time one-hour slot at 9pm on Christmas Day.
But the Yuletide special of the popular BBC One comedy The Royle Family could also prove to be one of the most expensive ever filmed, it emerged yesterday, after a mystery fault with the camera equipment turned it into a £100,000 farce.
The first few days of filming passed off without incident, but to the horror of the show's producers, when the film came back from the processing laboratory they discovered that all of the cast members' heads had been cropped out.
Phil Mealey, the writer of the Bafta award-winning series, said the mistake was "like going to Boots with your wedding snaps ruined, but on a massive scale".
He said: "When we looked at the footage, it was like my holiday photographs – everyone's head was cut off. Everything was lost. We were absolutely gutted. The camera had been checked and what was coming through on the monitors in the studio was fine. But a ground glass piece or something had dropped in the lens."
The problem meant that the stars of the programme, who include Caroline Aherne, Ricky Tomlinson, Craig Cash and Sue Johnston, had to be reassembled at the studios in Salford, Greater Manchester to film everything again.
"It was one of the most expensive rehearsals in the history of television. I've spoken to quite a few people and nobody has ever experienced that amount of footage completely lost," Mr Mealey said.
He added that the loss of the two days' of filming was likely to have cost his co-owned independent production company, Jellylegs, up to £100,000.
Last year, about 11 million people tuned in to watch The Royle Family Christmas special. This year's episode, which is entitled "The Golden Egg Cup", sees the sofa-bound Royle patriarch Jim and his stressed wife Barbara celebrate their 50th wedding anniversary with a Twiglet and Scotch egg-fuelled party – and by going on a caravan holiday.
"The first scenes shot on a Saturday and Sunday were of the party, and they were the ones with the most people in them. But the developing baths in London aren't open at the weekend," explained Mr Mealey.
But on Monday, the show's producer John Rushton returned from London bearing some terrible news. "We were about to shoot the third day and he said, 'Look, hold everything. I think we might have a problem with the camera'," said Mr Mealey.
By that time, Jessica Hynes, who plays Cheryl Carroll in the show, had already returned to London where she was appearing in The Priory at the Royal Court Theatre. There was no option but to bring her back to Salford, where she was reunited with the other members of the cast for an intensive day of filming.
"All that kind of thing is insured in the event of something happening. It's just one of those things. You have to pick yourself up and say, 'Right, OK, we've lost it.' And we're delighted with the finished product. There are some very funny scenes in it," Mr Mealey said.
The show ran for three series between 1998 and 2000, and since then there have been two special episodes, one in 2006 and another in 2008.