The Gavin and Stacey special attracted the largest Christmas Day audience in more than a decade.
As reported by Overnights.TV, a staggering 12.3 million people tuned in to show's long-awaited final episode.
The series returned to BBC One on 25 December for a 90-minute one-off episode, five years after the last Christmas special ended on a cliffhanger with Nessa (Ruth Jones) proposing to Smithy (James Corden).
That 2019 special was the top-rated show of the year, attracting an audience of 11.6 million, which eventually grew to a consolidated figure of 18 million.
This year's special - titled "The Finale" - is expected to beat that once the catch-up figures are accounted for.
After waiting five years, fans were not left disappointed by the episode with several praising it as the "perfect" conclusion to the series, which began in 2007.
In her review, O'Sullivan wrote: "This Christmas special is about half an hour too long and the script recycles the least interesting elements of what's gone before, but it still makes for lovely festive telly."
She also lamented the lack of "spice" in the episode. "As fans of the series will know, Gavin's parents reinvigorated their love life by dressing up as Charles and Camilla (Mick enjoyed wearing strap-on-ears). Perhaps for obvious reasons, the special is more risk averse," said O'Sullivan.
The new Wallace and Gromit film also attracted a large audience, with more than 9 million people tuning in to watch the duo's latest adventure.
In a four-star review of Vengeance Most Fowl, film critic Clarisse Loughrey wrote: "Vengeance Most Fowl sees Aardman return to their tried-and-tested formula.
"Yet, it's also the source of the studio's continuing brilliance - somehow, the familiar always feels new, and the craftwork never tires.
"If their new feature preaches that we can embrace technology without becoming reliant on it, then Aardman certainly puts its money where its mouth is."