Call the Midwife fans this is not a drill! The BBC has finally announced all the details we need to know about the new prequel series as the show begins filming.

Last year it was confirmed a Call the Midwife prequel of some kind would be arriving on our screens, and now it's been announced the new three part Christmas special series will be Call the Midwife: Sisters in Arms. The spin-off will be set in Poplar in 1939 and feature younger versions of the beloved characters we've spent the last 14 years getting to know.

Here's all the crucial details you need to know about the new series.

What will happen in Call the Midwife: Sisters in Arms?

The most recent series of Call the Midwife ended in 1971, however for this prequel we'll be going back to the late 1930s as war descends on Britain and be reunited with the younger versions of the nuns we've grown to love and some new midwives too.

Here's the full plot of what we can expect, according to the BBC synopsis: "In September 1939, Sister Monica Joan is in her prime, Sister Julienne and Sister Evangelina are young and zealous, and Nonnatus House is the beating heart of Poplar. Together with Sister Alice, and local GP Dr Kit, the nuns dedicate their lives to mothers, babies and the poor. But there is no gas and air, no penicillin, no cure for TB, and no welfare state. Then war is declared - and life gets even harder.

"The three young secular midwives who complete the team - Sybil, Olive and Marianne - receive a baptism of fire as the blackout and the Blitz take hold. While bombs rain from the sky, women give birth underground, families are shattered, children run wild, and whole streets are reduced to rubble. But courage, compassion and resilience triumph as the community unites in its efforts to survive."

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Given the most recent series saw the sad death of Sister Monica Joan, we are so delighted the prequel will give us a chance to be reunited with the fiesty nun, who we have never really gotten to see working as a midwife.

And we're not the only ones happy about her return, series creator Heidi Thomas said of the prequel: "I thought I had cried all my tears when Sister Monica Joan died, at the end of Call the Midwife’s 15th series. But the thought of her back on her bike, cycling through an air raid, set me off again, as did images of young Sister Julienne shaking when the sirens sound, and Fred Buckle still in his 20s, black with soot and sweat as a volunteer fireman. Then I'd be laughing at Sister Evangelina, in her element as an Air Raid Warden, or the juvenile Dr Turner turning up at a dance and being shy with girls.

Sisters in Arms has been a joy to write - like returning to the family home and finding all the people I have ever loved made young again and filled with new energy. I can't wait to start filming and look forward to sharing our new show with Call the Midwife’s fantastic fans.”

Ultimately we can expect a lot of tears, laughter and tense birth scenes that we've come to expect from Call the Midwife, but with the added threat of a world war looming.

Thomas added: "Call the Midwife: Sisters in Arms is about what happens when women go to war. It is about love and birth, separation and courage, lipstick and nylons (or the lack thereof). But it is also a medical drama, set in a devastating landscape where even the nurses cannot know if they will live till morning."

Who are the cast and characters of Call The Midwife: Sisters in Arms?

As the series is set many years before the most recently aired edition, we can expect a whole new cast to be taking on these beloved characters. The only cast member from the current series appearing in the prequel will be Sister Julienne actress Jenny Agutter, who will narrate the new series.

Here's who else you can expect to feature in the series and who they'll be playing:

  • Julie Hesmondhalgh as Sister Alice
  • Amy Booth-Steel as Sister Evangelina
  • Helen Schlesinger as Sister Monica Joan
  • Helena Wilson as Sister Julienne
  • Bally Gill as Dr Kit Malhotra
  • Martin McCann as Tommy Moffat
  • Rachel O'Connell as Mary Moffat
  • Liv Andrusier as Marianne Siegler
  • Lizzie Back as Sybil Maxted
  • Ellie Mckay as Olive Dobbs
  • Ciaran Bowling as Fred Buckle
  • Ami Metcalf as Betty Buckle
  • Ben Rose as Dr Patrick Turner

When will Call the Midwife: Sisters in Arms be released?

It's quite possibly the best Christmas present, as the new three-part prequel series will air this Christmas.

The exact dates have not yet been confirmed, but there is usually an episode of Call the Midwife on Christmas Day itself, so we would imagine at least one of the episodes will air on 25th December.

Is it too soon to wish it was December?