"Christmas is coming. The goose is getting fat and Fred is putting on his Santa hat," says Call the Midwife's Cliff Parisi, 63, who plays Fred Buckle in the charming BBC programme.
"He's back again - or at least I am - for the 21st year. I think I've been Santa on the BBC for 21 years on Christmas Day - first in EastEnders and now Call the Midwife. So, I am BBC Santa!"
That image of lovely, jolly Fred in his Santa suit is emblematic of Christmas Day for many of us, as Call the Midwife has cemented itself as a festive staple for the dark Christmas evening after a day of food and fun.
Naturally, the midwives and nuns of Nonnatus House will be back on our screens this Christmas Day, bringing with them a festive tale of community and social commentary on life in Poplar as 1968 becomes 1969.
"This is very much Christmas at home at Nonnatus, but it doesn't at all miss that whole magical sense of Christmas," says Jenny Agutter, 70, who plays Sister Julienne.
"It is quite a special Christmas for everybody. There is something in there which is going to be a surprise to everybody... It was a lovely surprise reading it. It's totally unexpected, there's quite a build-up to it - and I can say no more."
"The Call the Midwife Christmas specials always pack so much in - there is all the festive love and treats that you always expect but there's a lovely central storyline," adds Stephen McGann, 60, who returns as Dr Turner.
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"Being as secret as I can be with it, the story is about somebody who society has rejected and how they have more to them than we think. It is about their struggles, their medical pains and their social pains which we try to help.
"It is incredibly moving, and contains a beautiful central performance, which I think everyone will love."
Fans of Call the Midwife enjoy how the programme combines emotional tales of the realities of life on the poverty line in East London with charming characters, beautiful costumes, and plenty of laughs and heart-warming storylines.
For more than a decade, the BBC drama has been tackling topical subjects and contemporary social and medical issues from the 1950s and 60s, intertwining the tough discussions with wonderful tales of love in all its forms.
This Christmas special is no different.
"There is an exploration of a new medication for fertility, which brings with it a mother who is expecting twins as a result, which is wonderful," explains Agutter of Sister Julienne's Christmas storyline.
"The birth all happens rather excitingly and it was quite something to film - there were a lot of people crammed in a very small space. I always enjoy childbirth scenes, but this particular one was a very difficult one to film; interesting but just a bit cramped."
"Sister Julienne is always worried about Nonnatus House, although we're in a pretty good place financially, and she's got ideas about the future," she continues.
"And the only other concern, as winter approaches, is Sister Monica Joan. Winter is tough, something you need to get through, and Sister Monica Joan feels she's not going to get through it and won't be there next year.
"She is very low, very depressed and it is up to Sister Julienne to help her see that there is no reason to believe these dark thoughts and that there is a great deal of vitality in her."
Also facing the darker realities of life this Christmas is Cyril, played by Zephryn Taitte, who moved to London from Guyana and fell in love with Jamaican nurse Lucille. At the end of the last series, however, Lucille went back to her home country after a devastating series of events took their toll on her mental health, while Cyril stayed in England.
The storyline in this Christmas episode, Taitte says, "kind of rocks Cyril's world, because he is confronted with a dire situation".
"It is to do with social housing, and people losing their homes, or people holding onto things that they can't let go of," says the actor.
"And these people aren't waifs and strays - they have contributed to society, to the war effort. It is hard for Cyril to see what is happening up close and personal.
"His faith in Jesus is what helps him to try and touch base with the people who have less than he does. He can see what is wrong and he wants to be able to fix it, even though he can't do much.
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"This dire situation really affects him and changes his understanding of life in England."
But it's not all doom and gloom for all of Poplar: Trixie and Matthew are celebrating their first Christmas together with Matthew's son, Jonty, as a family, following their marriage last series.
"It's a very special time as it's the first time that they've really come together as a family unit," says Helen George, 39, who plays Trixie.
"Trixie's brother (Geoffrey) is back for this episode and it was so much fun to continue that story. Christmas and Geoffrey just go together really well!"
"Christmas is quite a hectic time for him," adds Olly Rix, who plays Matthew.
"I think he'd like nothing more than to have a quiet, family-orientated Christmas with his wife and son, but things don't quite turn out that way."
Set to be filled with laughter, tears, drama, fun and mayhem, the Call the Midwife Christmas special looks to be reflective of all the emotions of the festive season - a fitting close to the festivities on the big day.
"It's so special that we've become part of the Christmas Day TV menu," says George.
"It's always a lovely thing when everybody sits down on Christmas Day and watches us, and then chats throughout the evening about it.
"It's a very special thing."
Call the Midwife is on BBC One on Christmas Day.
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