Gavin and Stacey star Laura Aikman's involvement in the last ever episode was so top secret that even her own family had no idea she would be in it - and she kept it a huge secret from them for months. Over 12 million fans of the BBC sitcom tuned into watch the series final on Christmas Day and they were all left in disbelief when a shock twist showed James Corden's character Smithy was preparing to marry girlfriend Sonia - played by Laura, 39. The last Christmas special that aired in 2019