The BBC is ramping up security on the 'Gavin and Stacey' set after a major leak.

James Corden was pictured holding his script which gave away a major plot point

James Corden was pictured holding his script which gave away a major plot point

The beloved sitcom is returning for one last episode this Christmas with filming currently underway, but bosses are having to be extra careful after a photo of co-creator and star James Corden holding his script on location at a department store accidentally revealed a big plot point.

An insider told The Sun newspaper: "Everyone is excited for the return of Gavin, Stacey, Smithy and the gang so naturally interest is at an all-time high.

"Every day fans are flocking to the filming sites in Cardiff and Barry Island to see the cast filming and take their own photos and selfies.

“It’s a challenge trying to keep key storylines under wraps but the cast have been reminded to be on alert.”

Now, the cast and crew - including Joanna Page (Stacey), Ruth Jones (Nessa) and Mathew Horne (Gavin) - have all been told to keep their scripts closely under wraps.

'Love, Actually' star Joanna recently admitted that having fans flock to the set during filming has made her "feel like a pop star".

Speaking to ‘EastEnders’ star Natalie Cassidy, 41, on their ‘Off The Telly’ podcast, the 47-year-old actress said: “It's mad. You pull up in the car and get out and the crowd just go ‘Wayyy’, and you genuinely feel like a pop star or something.

“So I'm enjoying myself for now, because I know that when it finishes I'll be going home to my four children, who'll be like, 'Mummy mummy can I have my tea, mummy I want this I want that,' so I'm enjoying being fussed over, because it's not going to last for long.”

Joanna has been having “so much fun” shooting in Wales with the rest of the cast, including Alison Steadman, 78, Larry Lamb, 76, and Rob Brydon, 59.

She said: “Oh my god it's so much fun. I'm laughing absolutely loads. It's just mad though, it's absolutely mad."