Gavin and Stacey's original baby Neil actor returning as character in Christmas special

Gavin and Stacey is returning on Christmas Day. (BBC/GS TV Productions Ltd/Tom Jackson)

Baby Neil is returning to the Gavin and Stacey Christmas special to be played by one of the actors who starred in the role as an infant.

James Corden has revealed it will be Oscar Hartland, one of the young actors who played Smithy and Nessa's son as a baby, returning to play a more grown-up version of the child when the programmes airs on Christmas Day.

Speaking on Zoe Ball's Radio 2 Breakfast Show, he said: "When we shot the last series of Gavin and Stacey, Nessa and Smithy had obviously had their baby, so we had, on set, two babies who would be Neil the baby, so if one was crying, we'd switch it out for the other one.

Read more: Ruth Jones warns some Gavin and Stacey fans will be disappointed by the Christmas special

"The actor who is playing Neil the baby is one of those babies."

Baby Neil was played by two baby actors in the third series. (BBC)

Nessa star Ruth Jones also shared that the other baby Neil actor, Ewan Kennedy, came to visit the set when they were filming.

Rob Brydon, who appears in the series as Bryn West, said audiences will "totally accept" the youngster is the son of the characters before joking that it could well be Jones and Corden's secret offspring.

The Christmas special will air on Christmas Day on BBC One at 8.30pm. (BBC/GS TV Productions Ltd/Tom Jackson)

The storyline of the special has been kept tightly under wraps as fans eagerly anticipate the return of the Wests and the Shipmans on Christmas Day.

Jones has previously detailed how she had to employ undercover tactics to find out if the house used for filming in Barry would be available again.

The actor explained how she thought going alone may attract suspicion, so took along her niece as a decoy and she was able to get in contact with the woman who owned the house again.