Gavin And Stacey star Laura Aikman has revealed her family only discovered she was returning to the BBC sitcom while watching the finale on Christmas Day.
The actress, 39, shared a video on Instagram showing her family screaming in shock as her character Sonia appears on screen for the first time.
Sonia, the ex-girlfriend of Neil “Smithy” Smith, played by James Corden, returns for the final Christmas special in a crucial plot twist that is revealed when they meet in a John Lewis shop to work on their wedding gifts registry.
One member of Aikman’s family can be heard shouting “press pause” while another tells her “you never told me”, to which Aikman replies: “We never told anyone”.
On the video she wrote “the moment my family realise Sonia is ruining Christmas again” and captioned the post “I take an NDA very seriously”.
She also shared a photo of a cast board of all the Gavin And Stacey characters which has a space missing where her picture would have been.
Aikman first appeared as Sonia in the last Christmas Day episode in 2019 when Smithy brought his girlfriend to meet his family and friends.
Things became tense when she did not get on with the group and left before Smithy could propose to her as he had planned.
Vanessa “Nessa” Jenkins, played by Ruth Jones, later got down on one knee to confess her own love for Smithy, but before he could respond to her proposal the episode ended on a cliff-hanger and fans have had to wait five years to find out his answer.
The 2024 festive finale teased viewers as it began with the family of Stacey Shipman, played by Joanna Page, and her husband Gavin, portrayed by Mathew Horne, preparing for a wedding.
Fans had been hoping it would be Smithy and Nessa walking down the aisle, but Wednesday’s special revealed Nessa’s proposal was interrupted before Smithy could give his answer and the pair never discussed it again.
Sonia has a number of “bridezilla” moments including criticising Smithy at the altar over his shoe choice.
Throughout the 90-minute episode, Smithy’s friends and family question if Sonia is the right one for him, with best man Gavin finally telling Smithy he thinks it is a mistake during the ceremony.
After many guests – including Neil the Baby, Smithy and Nessa’s teenage son – stand up when asked if anyone objects to the marriage, Smithy realises he has to confess his true love and leaves Sonia a jilted bride as he races to Southampton to find Nessa.
Corden and Jones co-wrote the show which aired on the BBC between 2007 and 2010.
In 2019, it returned after almost a decade for a Christmas special, with the creators saying the 2025 episode would be the finale.
The documentary Gavin And Stacey: A Fond Farewell will be shown at 7pm on New Year’s Day on BBC One and BBC iPlayer.
