It’s back this Christmas … for the final time. But how did the naughty, surreal sitcom charm Britain so much that new episodes are a national event with viewing figures akin to a royal wedding?

The last time Gavin & Stacey was the centrepiece of the Christmas schedules, in 2019, 11.6 million people watched it, then annoyed each other for the rest of the night by shouting “Oh” and “What’s occurin’” in accents so far from Barry that search parties were sent out to find them. By the time catchup and streaming figures were included, that figure had grown to 17.1 million. Getting so many people to agree to watch anything together is now a feat so rare it’s usually reserved for football, royal weddings and lockdown announcements. But somehow, a comedy about a normal couple from different parts of the UK, and their slightly less ordinary family and friends, has become a momentous national occasion.

The last Christmas special bowed out with a cliffhanger, as Nessa told Smithy “I loves you, with all my heart,” then went down on one knee and proposed. Smithy’s shocked face, followed by a brutal cut to the credits, left everyone hanging. Now, five years later, at 9pm on Christmas Day, we will find out what he said. According to its writers and stars Ruth Jones and James Corden, this hour-and-a-half special really will be the last ever episode. In May, Corden shared a black-and-white photograph of him and Jones holding up the script, with “The Finale” very clearly right there in the title. (If that isn’t enough proof, on New Year’s Day BBC One is showing a documentary called A Fond Farewell, another title it will be hard to walk back.) “It’s all starting to get very emotional,” said Corden at the start of December.