Gavin And Stacey co-creator James Corden has said the series finale will explore Nessa's "chequered life".
The BBC sitcom is returning for a one-off festive special set five years after the 2019 Christmas Day episode that ended on a cliffhanger when Vanessa Shanessa "Nessa" Jenkins (Ruth Jones) proposed to Corden’s character Neil "Smithy" Smith.
Speaking on the podcast Table Manners with Jessie and Lennie Ware, Corden said: "It’s one of the best pieces of acting, what Ruth did with that character.
"The show picks up five years after we left off… Nessa has had this unbelievable chequered life and you find out more about that in this special - some really fun bits that we wrote."
At the end of the 2019 Christmas special, which won the impact award at the 2020 National Television Awards, Nessa tells Smithy: "I loves you with all my heart."
Speaking about this, Jones said: "The reason I feel it’s so emotional is because me and James have been on this journey for a long time.
"We’ve known each other since 2000 doing Fat Friends and because Gavin And Stacey has been such a massive part of our lives and that was going to be the last episode - we filmed that scene in the middle of the night as we were filming during summertime but it was set at Christmas so it had to be dark.
"We were there, just the two of us, on that road that had meant so much to us and I just, as Ruth, was looking at my dear friend James and when I said 'I loved you with all my heart’ I was saying it to you (James)."
The pair also revealed they revisited a hotel they had written part of the series in while writing the new special.
Corden, 46, said: "It’s tired now (the hotel)… those 16 years have not been kind.
"I think it’s under new ownership… We got there and lasted about an hour and then went to a different hotel."
Jones, 58, said: "I’m quite amazed we get any writing done at all.
"We talk a lot and start off the session by talking about gossip or life stuff and how we’re feeling.
"Sometimes that can go on for quite a long time and then we get a little bit of work done.
"The day needs a lot of ingredients - it needs naps, ingredients, and chocolate."
In the special, Gavin and Stacey "are looking for new ways to spice up their 17-year marriage", according to the BBC, while Nessa starts "a new business venture".
Corden said: "On TV or films, you very rarely see people that look like Ruth and I fall in love.
"You just don’t. I’d be dropping off a TV to Hugh Grant in Bridget Jones and Ruth’s like working on a newsstand when someone buys a newspaper.
"What I like about the show is that it’s so messy and complicated and they just clearly have fantastic sex. I really enjoy that confidence."
Discussing the final episode, he added: "It can’t carry on. When you’ll see it, you’ll know."
Speaking on a potential spin-off, he continued: "We don’t know if we have another idea in us but I can honestly say that if we didn’t attempt to try and even explore the idea of writing together then I’d be so disappointed."
In the sitcom, Mathew Horne and Joanna Page play lovers Gavin and Stacey, Alison Steadman is Gavin’s mother Pam, Larry Lamb is his father Mick, Melanie Walters portrays Stacey’s widowed mother Gwen, and Rob Brydon plays her Uncle Bryn.
Former chat show host Corden revealed in July that he and Jones had finished writing the script for the final episode. The BBC announced filming had wrapped in October.
The documentary Gavin and Stacey: A Fond Farewell will be shown at 7pm on New Year’s Day on BBC One and BBC iPlayer.
Source: Press Association
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