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The cast and crew had to be called back to refilm the ruined scenes of 'The Golden Egg Cup' episode at an estimated cost of £100,000 ($135,000).
Co-writer Phil Mealey told The Telegraph: "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."
According to Mealey a tiny object had somehow dropped into the lens completely ruining two days of filming.
He added: "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. It was like going to Boots with your wedding snaps ruined but on a massive scale.
"We had to drag everyone back to film it again. It was one of the most expensive rehearsals in the history of television.
"I've spoken to quite a few people in TV and nobody has ever experienced that amount of footage completely lost."
It meant that the cast and crew had to be recalled, but to add even more drama to the situation, Jessica Hynes - who plays next door neighbour and Denise's best pal Cheryl - had gone back to London where she was appearing in a play.
However, they managed to pull it off and, as we all know, the episode went out and was pretty brilliant.
Mealey added: "All that kind of thing is insured in the event of something happening like that.
"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."
And that isn't the only balls up The Royle Family Christmas specials have been faced with, in one episode one of Jim's testicles had to be edited out of a scene.
In the episode, Jim (played by Ricky Tomlinson) is carried up to the bathroom by son Anthony (Ralph Little) and Dave (Craig Cash) and one of his balls ended up popping out.
Appearing on Loose Women, Tomlinson explained: "She [co-creator Caroline Aherne] said, 'when we were watching the rushes one of your testicles was hanging out. One of your testicles was hanging out the side of your underpants!
"'It's cost the BBC a fortune to get it edited out, what do you say about that?'"
To which he replied: "I said, 'Well, was it the big one or the small one'?"
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