“Gavin & Stacey: The Finale” has broken viewing records in the U.K. since airing on Christmas Day.

According to the BBC, the final episode of the hit British sitcom — co-created by Ruth Jones and James Corden — is now the U.K.’s most-watched scripted show across all broadcasters and streamers since current records began in 2002. As per the latest data, ratings have already reached 19.3 million, smashing its own record from the 2019 “Gavin & Stacey” Christmas special, which reached 18.5 million in 28 days.

Watched by 12.3 million on Christmas Day — the biggest overnight for the day since 2008 — “Gavin & Stacey: The Finale” has since added more than 6 million to that total and it well on track to surpass 20 million views when the 28-day figures are published. Of the 19.3 million, 4.2 million are aged 16-34, making the episode the highest young audience for a scripted show since 2002.

“We are completely overwhelmed by the audience response to...