Actors in the Christmas special of Call the MidwifeCredit:Coco Van Oppens/BBC/Neal Street Productions/ Call the Midwife writer Heidi Thomas, who has previously tackled the thalidomide scandal, backstreet abortion, domestic violence and the Pill, said she deliberately wanted to move the show’s Christmas audience to anger.She said: “A lot of people used to think Call the Midwife was about nostalgia, but we’re constantly trying to push the envelope in tackling of social issues.“We often tell the story of people who are in a minority and it says something about the British viewing public that a minority subject ges a majority audience.”Thomas added: “We have a passion for the way history well told can reflect the way we lived our lives. That passion leads to compassion. Passion, compassion and anger are all there in our Christmas story.”The Christmas specials sees sister Julienne and her team travel to the struggling Hope Clinic in an attempt to get it back on its feet. Along the way they tackle a polio immunisation programme for rural children, caesareans performed by candlelight and contaminated water supplies.They are soon confronted by the realities of Apartheid’s iniquitous racial laws.And just as the East End based episodes do, so the Christmas special turns on an old fashioned sixpence from happiness to anger, joy to pathos. When Tricia and Barbara dance in the moonlight with two expectant black mothers to a record they’ve brought from London, their shared happiness is brought to a halt by a passing police patrol who deem it an “illegal gathering”.One of those women tells how the hated Apartheid pass laws forced her to quit her job as a secretary in the city and return to the poverty of her village.But anger is also leavened by humanity, such as in the dispute over access to clean water, where it is discovered that personal loss is as much a motivator as white racist hatred.The cast of the show have revealed their shock at the economic inequalities still present in post-apartheid South Africa.“The inequality that remains a legacy of apartheid is massive. It’s a reminder that the life we live in London is like paradise compared to that,” said Charlotte Ritchie, who plays Barbara.Victoria Yeates, who plays Sister Winifred, added: “You have the poverty of the townships and ten minutes away, where our hotel was, it’s like Malibu or Beverly Hills. In the townships I felt embarrassed about getting my iPhone out.”Indeed the case said that having worked amid the poverty of the post war East End the characters they play may well have been more prepared for the hardship they found than their modern counterparts.“It’s worth remembering that the East End at that time was pretty dire for a lot of people,” said Ritchie. “When they arrive in South Africa they are not as shocked as you might imagine because of the poverty they have seen in London.” They have struggled with the impact of society’s ills on the lives of working class women and children in London’s East End, from the end of the war to the start of the Sixties.Now the midwives and nuns of Nonnatus House in Poplar are to be confronted with the horrors and injustice inflicted on black South Africans during the Apartheid-era.A fateful phone call for help from a rural clinic near Cape Town will see Sister Julienne, Sister Winifred, Trixie, Barbara and their colleagues faced with unprecedented new challenges for a Call the Midwife festive special, to be broadcast on Christmas Day.And once again the writers and producers of the BBC One drama have not shied away from shining a spotlight on some of the more controversial issues of the day – including the institutionalised racism which condemns the team’s patients to poverty and substandard health care. It was revealed last week that the BBC has commissioned Call the Midwife for a further three series.Which means that having confronted Apartheid, Sister Julienne and the occupants of Nonnery House will now be forced to marshall their spiritual and medical efforts to tackle the fall out from the social changes wrought by the mid-sixties and seventies.But whatever problematic issues lie at the at the heart of the Christmas special, and the forthcoming series – which is due to begin broadcast in January – the compassion of Poplar’s nuns and midwives and nuns continues to shine through..“We’re dealing with difficult subjects,” said Linda Bassett, who plays Phyllis Crane. “And out of that comes love.”Call the Midwife Christmas special is on BBC One on Christmas Day. We have a passion for the way history well told can reflect the way we lived our lives. That passion leads to compassionCall the Midwife writer Heidi Thomas Sister Winifred (Victoria Yeates) and Nurse Crane (Linda Bassett) help deliver a baby in South Africa Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.