The highly anticipated Call The Midwife spin-off, Sisters In Arms has finished filming, and the series creator has revealed that making the show left the cast and crew "in tears." The three-part prequel will air during the next festive period, in place of the usual Call The Midwife Christmas special. Clearly enthusiastic about the spin-off, Heidi Thomas says, "Oh we have SUCH a lot to show you!" We certainly won't be, and will be counting down the days to the Sisters In Arms release date, along with other Call The Midwife fans everywhere. Sisters In Arms will air on BBC One and BBC iPlayer during the Christmas period, with no official release date set at this time.