Call the Midwife has become one of the BBC's biggest hits at Christmas - meet the nuns and nurses at the heart of this festive favourite.
This year, EastEnders legend Anita Dobson guest-stars in the Christmas Day special. Find out about her role and much, much more below.
Valerie Dyer (Jennifer Kirby)
One of the most recent additions to Nonnatus House, former war nurse Valerie will face a bitter challenge in this year's Christmas special.
Jennifer Kirby made her British TV breakthrough on Call the Midwife, but she had an impressive stage career with the Royal Shakespeare Company before joining the BBC1 drama.
Nurse Barbara Hereward (Charlotte Ritchie)
Nurse Barbara is now a much-loved member of the Nonnatus House team, and is happily married to her husband Tom. But will the new couple want to stay in Poplar forever?
Charlotte Ritchie is a rising comedy and drama star, having appeared in Channel 4's Fresh Meat and BBC3's Siblings before landing a regular role on Call the Midwife.
Rev. Tom Hereward (Jack Ashton)
The dashing vicar made quite the impression when he first arrived in Poplar, and was for a time engaged to Trixie. However, after she broke it off, Tom started dating Trixie’s colleague Barbara Gilbert. The pair are now happily married, and now he is looking to the future...
Jack Ashton joined the cast during series three and has previously starred in an episode of Broadchurch, Vicious and Holby City.
Nurse Trixie Franklin (Helen George)
Nurse Trixie is hoping to escape to the slopes for Christmas with beau Christopher Dockerill – but the weather may scupper their plans...
Helen has starred in Call the Midwife from the beginning. The actress also appeared in the 2015 series of Strictly Come Dancing.
Shelagh Turner (Laura Main)
Shelagh Turner is trying to take it easy after giving birth to baby Teddy – but she's finding it hard not being able to help her husband Dr Turner at his surgery.
Scottish actress Laura Main first appeared on the stage at the age of 11 in a stage production of The Sound Of Music. As well as a lengthy career in theatre, she featured as DC Alison Bain in ITV's Murder City.
Dr Patrick Turner (Stephen McGann)
Life is good for Dr Turner and his family, with wife Shelagh giving birth to a baby boy. But he will be busier than ever in the extreme cold weather.
Stephen McGann is married to Call the Midwife screenwriter Heidi Thomas. He also has a close connection to his Midwife character, having studied for a Masters degree in Science Communication.
Sister Julienne (Jenny Agutter)
The most experienced midwife at Nonnatus House, Sister Julienne is the consistent stalwart among the midwives.
Jenny Agutter starred in the classic movie version of The Railway Children when she was just 18 – she had already appeared in the BBC's TV adaptation of the novel. Since then she's won a Bafta for her performance as Jill Mason in the 1977 film Equus and played Tessa Phillips in Spooks.
Nurse Phyllis Crane (Linda Bassett)
The long-serving Poplar nurse is as dogged and dedicated as ever, even when the Big Freeze stops her in her tracks...
Linda Bassett played Julia Roberts' mother in the film Mary Reilly, and was nominated for a Bafta for her performance as Ella Khan in East Is East. Past TV credits include BBC period dramas Sense and Sensibility and Lark Rise to Candleford, and in recent years she's starred in Calendar Girls and The Reader.
Sister Monica Joan (Judy Parfitt)
Monica was one of the first women to qualify as a midwife in Britain. Now retired and suffering from dementia, she lives full time at Nonnatus House and is a She is the beloved mentor of all in Nonnatus House.
Judy Parfitt has been twice nominated for a Bafta: for her performances as Maria Thins in Girl With A Pearl Earring and Mildred Layton in The Jewel In The Crown.
Fred Buckle (Cliff Parisi)
Handyman Fred is married to Violet, and have recently been joined by orphaned young man Reggie, who has Down's Syndrome.
Cliff Parisi spent eight years in Eastenders playing the role of Rick 'Minty' Peterson. Since leaving Albert Square in 2010, he's been a regular face on Call The Midwife and appeared in the final series of BBC comedy Outnumbered.
Violet Buckle (Annabelle Apsion)
Widowed shopkeeper Violet married Fred in series four, and the pair have had a new lease of life after taking young Reggie under their wing.
Annabelle Apsion is best known for her starring role in Channel 4 comedy Shameless. Recent TV appearances include period dramas The Halcyon and The Village, and hit ITV drama Doc Martin.
Reggie Jackson (Daniel Laurie)
Reggie first appeared in series six, after the nuns at Nonnatus stepped in to help him after his mother died. He has Down's Syndrome, but is embraced by Fred and Violet and becomes a firm favourite of the Poplar community.
Actor Daniel Laurie has appeared in both Call the Midwife and Sky 1 comedy Stella, and led the cast of BBC Radio 4 Charles Dickens adaptation Barnaby Rudge.
Sister Winifred (Victoria Yeates)
After living most of her life in the countryside, Sister Winifred came to Nonnatus House as quite an innocent young woman. Over the past few series she has grown in confidence.
Victoria joined the cast of Call the Midwife for the drama’s third series in 2014. Prior to starring in the show, she had taken on small roles in Lip Service and Holby City.
Mabel Tillerson (Anita Dobson)
Mabel Tillerson has lived a hard life with her husband Percy, and has never really socialised with the other tenants in her apartment block. What is she hiding?
EastEnders star Anita Dobson makes a triumphant return to Christmas Day TV, having made TV history as Angie Watts. Her Christmas Day 1986, when 'Dirty Den' served her her divorce papers, was watched by over 30 million people.
Sergeant Woolf (Trevor Cooper)
Nurse Crane may have finally met her match in the gruff, decidedly unfestive local policeman Sgt Woolf.
Trevor Cooper has become a BBC3 hit thanks to starring in comedy This Country alongside his brother Paul. The series is written and created by his niece and nephew Daisy and Charlie Cooper. He's also had roles in series including Doctor Who, Outnumbered, Inside No 9 and more.