Gavin and Stacey star set to make a huge surprise appearance in character during the Strictly Come Dancing final

Strictly Come Dancing fans are going to be left shocked during Saturday's finale as Gavin & Stacey favourite Nessa is set to make a surprise appearance. 

Insiders have revealed that actress Ruth Jones is set to transform into her Welsh sitcom character to read out the voting terms and conditions during the live final.

Ruth will perform the short skit during the competition ahead of the highly-anticipated final episode of Gavin & Stacey airing on Christmas Day. 

The appearance will come as celebrities JB Gill, Sarah Hadland, Tasha Ghouri and Chris McCausland battle it out to lift the Glitterball Trophy.

A source told The Sun: 'The BBC have gone all out with their Strictly surprises this year — and having Ruth in as Nessa is the cherry on the cake. 

'Last Saturday they had Wallace and Gromit read the Ts and Cs for voting, and Ruth will be doing a skit as Nessa this week.

'The BBC have worked really hard to get these off the ground and it’s a great cross-promotion for what will be their two biggest shows at Christmas.

'Strictly fans loved seeing Wallace and Gromit and the BBC think they’ll be thrilled when Nessa pops up on Saturday night.'

It comes after Gavin and Stacey creators James Corden and Ruth issued a major update with their co-stars on Tuesday.  

The duo joined Zoe Ball for the BBC Radio 2 Breakfast: A Gavin and Stacey Takeover ahead of the sitcom's final ever episode. 

James and Ruth were joined by Joanna Page, Mat Horne, Rob Brydon, Alison Steadman, Larry Lamb and Rob Wilfort for the three hour long special. 

During the show they revealed secrets about the upcoming finale, shared some of their favourite memories from the series and discussed all things festive. 

Die-hard fans have been speculating about how the co-creators will round off the show, with the duo giving an insight on Monday. 

Many questions remain unanswered since the last episode, including what happened after Nessa's shock proposal to Smithy. 

While the plot for this year's Christmas special still being kept tightly underwraps, Ruth has revealed that they are definitely bring the sitcom to an end.

Speaking in an interview with The Big Issue she said: 'I keep telling people this finale might not be what you are expecting. And I guarantee we will definitely not be coming back.'

James added: 'What people are going to see on Christmas Day is the culmination of a 20-year love story, which hopefully shows, if nothing else, that love is complicated and messy and for everyone.' 

Elsewhere, one Gavin and Stacey star has confirmed that they will be appearing in the highly-anticipated Christmas special and dropped a major hint about the final scene.

Steffan Rhodri, known as Dave 'Coaches' Gooch on the show, has revealed a small spoiler about the final episode.

Speaking to Metro, he said: 'My character Dave is a bit of an outsider but they planned it so that with the last scene we did, which is the ending, we were all together and it was very touching.'

He added that he can't say anything else about the Christmas special, but he can confirm that he will be in it.

Steffan missed the 2019 Christmas special, meaning he hasn't filmed for the show in 17 years.

He said: 'I actually enjoyed it more than I thought I would. It was like putting on a pair of old trousers. It was really lovely to hang out with them again.'

Fans know coach driver Dave for his iconic line about what he will and wont put up with on his coach - 'fags and weed, glue and speed, but I draws the line at crack'.

But what they may not know is that Steffan based the character on his uncle who is a coach driver with a similar attitude. 

The Gavin and Stacey Christmas Special airs at Christmas Day at 9pm on BBC One and BBC iPlayer.