Call the Midwife spin-off Sisters in Arms has shared an exciting filming update, confirming that production has wrapped. BBCCreator Heidi Thomas noted that the franchise "has a long and noble history of filming Christmas specials during heatwaves", joking that they "welcomed the snow-machine back to the Nonnatus House set like an old friend". "But I was surprised how many new emotions Call the Midwife: Sisters in Arms sparked," she reflected on filming. As well as the new stars, original Call the Midwife Sister Julienne actor Jenny Agutter is part of the cast as the narrator. Call the Midwife: Sisters in Arms airs this Christmas on BBC One.