The Gavin and Stacey Christmas special was the UK's most-watched scripted TV programme of the 2010s, new audience figures show.
In total, 17.1 million viewers tuned in to the comeback episode live or on catch-up during the subsequent week, according to the consolidated ratings.
Only sporting events and the 2010 X Factor final were watched by more people during the past decade.
And it was the most-watched comedy since Only Fools and Horses in 2002.
Del Boy and Rodney's penultimate Christmas Day special was watched by 17.4 million people, according to ratings body Barb.
The new episode of Gavin and Stacey, written by and starring James Corden and Ruth Jones, was the centrepiece of BBC One's Christmas schedule and revisited Gavin, Stacey, Smithy, Nessa and their clans nearly 10 years after they left our screens.
The BBC said there had been 4.4 million requests for the programme on iPlayer, including 1.4 million from viewers aged 16-34 - a record first week for any episode.
Gavin and Stacey began on BBC Three in 2007 and ran for three series until 1 January 2010. At that time, the then-finale was watched by 10 million people.
The comeback episode's success - and its cliffhanger ending - have left the door wide open for another visit to Barry Island in the future.
Oscar Hartland, 10, who played Neil the Baby both during the original run and in the new Christmas special, said James Corden had told him the show could return.
"I did ask James in the process of filming but he said, 'It's just [whether it's] what the people want'. Me, I would love it to happen. It really depends what other people think about it and if they like it or not."
Jones told The Sun it was "complicated" to get together to write with Corden, who now hosts a late-night talk show on US TV network CBS.
"I do say never say never, as while we did make it work that was after three years of trying to find time when we could sit down and write it," she said. "Obviously with the way it ends, there is room for more."
Commenting on the ratings, BBC director of content Charlotte Moore said: "Gavin and Stacey has been a phenomenal hit this Christmas breaking records to become the biggest scripted show of the decade, and the biggest first week for any episode on BBC iPlayer for young audiences ever.
"Congratulations to James Corden, Ruth Jones and all the team."
Director general Tony Hall said the BBC iPlayer had received more than 100 million requests in total over the Christmas week - up by more than a third compared with the previous year.