Rob Brydon reveals the 'Gavin & Stacey' cast had a WhatsApp group chat code name to keep the Christmas special a secret.

Rob Brydon

Rob Brydon

The popular BBC sitcom will be back on December 25 for a one-off return, and the 54-year-old actor - who will reprise his role as Uncle Bryn - admitted his co-star Alison Steadman (Pam) came up with the pseudonym at an awards ceremony.

He told the Mail on Sunday newspaper's EVENT magazine: "She came up to me asking me if I could believe it, and she was so excited about 'Gilbert and Sullivan'.

"I'm a bit thick so I didn't get it at first. I thought she'd been in a drama that I'd missed so I actually told her I'd seen it and hoped she'd get an award.

"It was only a few minutes later I realised what she meant. I think we were all so stunned and so desperate to keep everything quiet."

Indeed, Ruth Jones (Nessa) - who was back collaborating with co-creator James Corden (Smithy) on the script for the special - admitted they even kept the reunion news a secret from their own parents.

She added to the publication: "We didn't even tell our mums. And I had to keep inventing reasons why I was going to Los Angeles to see my friends.

"We couldn't be pictured together because the whole world would start thinking, 'Oh yes... 'Gavin & Stacey' is back'. We said absolutely nothing to anyone."

The sitcom - which aired on the BBC for three series, plus a Christmas special, from 2007 to 2010 - stars Mathew Horne and Joanna Page as the titular Gavin and Stacey.

Meanwhile, James previously admitted he feared they were being "naive" about plans for a one-off revival when they were struggling with the script almost a decade after the show came to an end.

He recently said: "We'd confused ourselves in thinking there needed to be an absolute narrative arc - there was so much in the story, there was no room for the characters to breathe.

"We'd written about 40 pages, and we sat and we read it ... and we both went, 'This just isn't good enough. It doesn't feel like the show. It doesn't feel like it's right.'

"There was a real silence in this room ... a sense of, 'Maybe we were too naive to think we could pick it up.' "