Just as we think we’re getting stuck into Christmas dinner at Nonnatus House, the nuns and midwives are packing their cases to ditch snowy Poplar for sweltering South Africa when they are sent to help a struggling mission hospital.

It’s a treat to see them shedding their traditional poise and really testing their resolve – new challenges range from a lack of clean water to a very unreliable hospital truck, as well as some emotive social problems.

There’s still time for a dramatic birth or two, though, while Sinéad Cusack gives a wonderful turn as dedicated but frosty Dr Myra Fitzsimmons, who runs the hospital, but may need a spot of medical treatment herself…