With its feel-good comic moments, medical marvels and tiny babies giving us new hope, BBC1's Call The Midwife has proved time and again to be perfect Sunday night telly.

When we last saw the residents of Nonnatus House - in the recent tear-jerking Christmas episode - the London borough of Poplar was buried in snow, as the Big Freeze of 1963-64 took hold.

Now it's series seven and, while the snow shows no sign of shifting, the team is facing lots of changes.

Here, the cast and writer tell us more.

A NEW TEAM MEMBER

New to the show is Leonie Elliott, who plays Lucille Anderson – the first West Indian midwife to feature as a regular character.

Leonie, 29, says she enjoyed shining a light on women who moved over from the Commonwealth to join the NHS, calling them “unsung heroes”.

“My aunt came over to England from Jamaica in the late 60s to study nursing, so there were synchronicities there,” says the actress, who has previously starred in shows such as Black Mirror. “I would speak to her about her experiences, because it’s nice to get someone’s perspective who lived through it.”

THE BIG FREEZE IS STILL CAUSING HAVOC

It’s a dramatic arrival to Nonnatus House for Lucille, when her plans to travel from Somerset, where she has been training, are disrupted by the continuing cold snap.

“She finds Somerset quite close to her rural upbringing in Jamaica,” explains Leonie of her character’s move to London.

“She just wants a bit more excitement and wants to go to the big city, but is met by a massive snowstorm. So, a far cry from Mandeville in Jamaica!”

RACIAL PREJUDICE IS ADDRESSED

Lucille finds herself in some challenging situations with patients who are less than accepting of her background, which Leonie admitted was quite difficult to film.

Writer Heidi Thomas, 55, says: “Obviously, one has to address these issues of racial prejudice whether they’re personal or institutional. But Lucille is so much more than that.

“We look a lot at her experiences of settling into a strange culture, finding a church that she feels happy in... and Lucille is sometimes quite old-fashioned in her moral point of view, which is quite unusual. It’s important that we see all those aspects of Lucille’s character.”

SISTER MONICA JOAN CONFRONTS THE AGEING PROCESS

The wonderfully eccentric nun, played by 82-year-old Judy Parfitt, is one of the most-adored characters in the show, and it sounds like we could be in for an emotional watch.

“I’ve created a storyline for Judy which is to do with her failing eyesight,” says Heidi. “That’s given us quite a slow journey across the body of this series, because it’s realistic. And I love writing about her.”

EXPECT MORE SOCIAL CHANGE

Jenny Agutter, who has starred as Sister Julienne since the show first aired, points out that the rapid changes in science and the arts, and then into society, were enormous in the 60s.

“Each year presents something different in the way of social changes,” says the 65-year-old.

“So, this series we have a stripper who gets pregnant; we’ve got somebody who is very frightened of giving birth, which is a very particular condition. There’s a sense that women are perhaps much more in control than they were. Although what I love is our props and magazines, the adverts are still very much women in their aprons in the kitchen. And so, it’s changed, but not that much.”

LOVE IS IN THE AIR FOR NURSE TRIXIE FRANKLIN

The fun-loving midwife has had some turbulent times, but in series six she fell for charming dentist Christopher – and this romance is set to continue.

“You see the effect of him being divorced with a child,” reveals actress and Strictly star Helen George, 33, who has played the unlucky-in-love character since series one.

“So, you see the complications of Trixie’s love for him and the love for the child. But, the relationship is progressing nicely.”

VALERIE DYER FINDS HERSELF IN A BEAUTY CONTEST

Jennifer Kirby, who joined as the former army nurse last year, admits such an idea seems jarring to us now. But, in the 1960s, it was “almost like the norm”.

“It’s a nice thing for the character, that she sort of throws herself into it, even though she might not seem like a beauty pageant sort of girl,” adds the 28-year-old actress.

IT’S HAPPY FAMILIES FOR SHELAGH AND DR PATRICK TURNER

After years of thinking she wouldn’t be able to conceive, the series six finale saw Shelagh Turner give birth to a baby boy.

“Her life has grown even more and become what she’d dreamed of,” explains Laura Main, 36, whose character Shelagh moves into a new home this series.

“We’ve got Tim who’s changing all the time and growing up, and we’ve got little Alice who’s just becoming more and more of a dream, and now we’ve got little baby Harry who’s just so cute. What Heidi has given me to play with, it’s a treat.”

A NEW AU PAIR TURNS HEADS

“She’s really gorgeous and really lovely,” reveals Laura.

“We do a couple of episodes with her, and it starts off quite comic – there’s a bit of fun to be had. Initially, I’m thinking, ‘Patrick, oh dear’, but then I think I’ve got to be more concerned about young Timmy having his head turned!”

Stephen McGann, who plays Patrick, says the au pair’s storyline gains more depth as the series goes on, adding: “Like anything in Call The Midwife, you get taken on a journey.”

Call The Midwife returns to BBC1 on Sunday January 21 at 8pm