Gavin & Stacey co-creator Ruth Jones has revealed she and James Corden almost gave up on their Christmas comeback episode after struggling to develop the story together.
The Welsh actress and writer, who also plays Nessa in the much-loved sitcom, said she and US-based Corden were not "match fit" while working together on the series for the first time in 10 years.
Jones, 53, told an audience in Cardiff on Monday the Christmas special had first been discussed two years ago, but she and Late Late Show host Corden, 41, hit difficulties while writing together in LA in February.
She said: "When we actually reached the point when we were able to announce it, it was such a huge relief because it had been such a big journey to get to that point.
"It wasn't easy that week because, bearing in mind we hadn't written it for years and years. We'd had ideas for characters, lines of dialogue, going back and forth, but we hadn't sat down and written a script.
"We weren't match fit anymore, where before we'd written series after series, three series' in a row.
"And you know James and I hadn't spent that much time together.
"We'd seen each other and spoken together, but we hadn't sat down and written for a long time.
"So there was a lot at stake.
"We got to halfway through the week... and we hadn't even got to halfway through the first part of the story.
"So there's a lot of rewriting, reshuffling, discussing.
"One night we thought, let's just give up, because it just didn't seem to be... I don't know, there was something missing and I couldn't pinpoint it.
"We had dinner with our partners, and we got talking, something sparked something off, that led one thing to another and, I don't know how it happened, but out of the blue we just got this idea and I think that was the heart of this Christmas special."
Jones also said she wrote a fake story line for the episode in order to prevent would-be leakers from spoiling the episode for fans, which she said had since been published online.
She was joined at the "Evening with" event alongside co-star Rob Brydon, who plays Uncle Bryn, and both said they would be watching the special with their families, while Brydon admitted watching old episodes on television.
Brydon, 54, said: "Often with things you've done you don't want to watch too much because all you see is what you do wrong.
"But with Gavin & Stacey it's such an ensemble and it's so good that, yeah, when we're flicking around at home and it comes across we often stay with it and watch it."