John, who played Stacey’s outrageous neighbour Doris in all three series of the BBC sitcom, died in 2011 at the age of 84.
Speaking at a screening of the one-off festive episode, actress Melanie Walters (who plays Stacey’s mother Gwen) revealed how the show’s art department kept John’s memory alive during the first read through of the new script.
“The art department gave me a picture of Margaret and myself from one of the episodes of Margaret and I sitting with these huge - I don’t know why they were so big - bright orange coats, and we were sitting reading the paper,” she said.
“Kyz [Kistell, art director] brought me this picture and I put it on the table as we read,” she added. “It was between me and Chris [Gernon, director].”
Ruth Jones, who co-wrote the series with James Corden and stars as Nessa, fondly recalled filming on Barry Island with Johns and Walters, joking that the duo had been like “giggling school girls.”
“One of my favourite episodes is when they all go to Barry Island for the Bank Holiday, that was 10 years ago, because that was such fun to film,” she said.
“Maggie was there and you two were like giggling school girls, weren’t you, all day, sat there under your sun hats.”
Jones praised her former co-star as “such a special woman and such an incredibly talented actress” and said that her “biggest sadness” was “not having [Johns] there” in the special.
“I hope, Maggie, you’re watching up there and having a good laugh and sharing it at Christmas with us,” she added.
The Gavin and Stacey Christmas special will reunite Jones and Corden with their co-stars Joanna Page (Stacey), Mathew Horne (Gavin), Alison Steadman (Pam), Larry Lamb (Mick) and Rob Brydon (Uncle Bryn).
Taking place 10 years after viewers said goodbye to the much-loved characters, the episode will see Uncle Bryn hosting a Christmas dinner in Barry for his niece and her Essex in-laws.
The Gavin and Stacey Christmas special will air on the BBC on Christmas Day.