Reggie's record-breaking Christmas paper chain captures the joy of Call the Midwife

Violet was nervous about whether it would all come together, but – with screenwriter Heidi Thomas presiding over the plot – of course it did. Fred Buckle (Cliff Parisi) soon rallied the community in the Outer Hebrides, and Reggie's idea inspired a frenzy of activity as nuns and nurses and Outer Hebridean families pasted together strips of newspaper and coloured paper ready for the big day in Poplar, arriving just in time to symbolically (and literally) link everything together.

"That's very Heidi," Nurse Crane actress Linda Bassett commented. "That chain linking people in different communities."

Christmas is "a gathering and a sharing of the things that matter most," said the voiceover of Vanessa Redgrave as she concluded the festive episode. But it's about even more than that.

Because Reggie, who has Down's Syndrome, is a fully-rounded character with his own hopes and dreams and sense of humour – and it is just so wonderful to see him in the Christmas feature-length special as the driving force behind a storyline that unites the whole community. His scenes with Miss Higgins (Georgie Glen) are particularly lovely; the eccentric GP's receptionist sees Reggie in a glum mood and finds a way to cheer up her young friend.

"The paper chains scene was amazing," Daniel Laurie said ahead of the Christmas special. "I got help from Miss Higgins... Miss Higgins had this love and support for Reggie, for doing the paper chains."

Georgie Glen added: "We had our moment together on that didn't we? It was really nice... It's a real thing of togetherness, isn't it?"

Perhaps Reggie is so well-written because Heidi Thomas herself had a brother, David, with Down's Syndrome. He died aged just 15, and she once told RadioTimes.com: “If there’s anything in me that’s kind or strong or good, it’s because of those childhood years when I had him as a vulnerable, funny, outrageous sibling.”

Thomas has always tried to be inclusive in Call the Midwife – and that's a huge part of what has kept viewers coming back for more each year. She writes characters who are able-bodied and characters who are disabled; she writes characters who are East End born-and-bred, and characters from different cultural and religious backgrounds. Racism and discrimination and hatred and sexism often crop up, but these prejudices are obstacles to be surmounted.

Dr Turner actor Stephen McGann, who also happens to be the screenwriter's husband, has a theory about the show's success – and he might just be correct.

"The paper chain thing - the idea of when all the strands came together into a paper chain... in very general terms, you're looking at a country asking itself about itself. What is it? What are people? Who are we?" he said, reflecting on the 2019 Christmas special.

"We travel to the other side of the island, we go right up to the north, and we go into another community and all through this community of all these different types of people, we're saying, who are we? We are literally, at the end of this episode, putting the same chain together. All of us."

Comparing dramas about "a different way for a serial killer to kill another human body and leave it on a beach" versus dramas about "how to bring the paper chain together," McGann suggested, "Maybe that's part of the answer to why this show is still around after nine series. Maybe it tells us something about what we hope, what we dream... it's historical but what it's really about is addressing what people really – their better instincts, the better reaches of their nature."

The Call the Midwife 2019 holiday special airs on PBS in the US on Sunday December 6 at 9/8c