Heidi Thomas on the longevity of Call the Midwife and season 12 plans

Luckily, it’s season 12 they’re currently shooting, she clarifies, and not the Christmas special – with production on the festive episode already having wrapped earlier this year.

Call the Midwife might have run for over a decade, but Thomas’s adaptation of midwife Jennifer Worth’s memoirs remains as popular as ever, so much so that it has been crowned the greatest television show of the past 25 years by RadioTimes.com readers, beating all sorts of genre juggernauts from the Doctor Who reboot to dramas like Succession and Netflix’s Stranger Things.

The long-running drama’s facade of cheerful nuns, nurses and new-born babies means it often gets dismissed as cosy end-of-the-week viewing. But the show, which began its story in 1957 and has since moved through the swinging '60s, also handles politics and subtly chronicles social change, putting women’s stories centre stage as society slowly evolves around them.

And it’s this shifting lens through which the female characters view the world which Thomas attributes to the show’s longevity.

“Series 12, which we’re filming at the moment, is set in 1968,” she explains. “Women’s lives were incredibly different. Abortion had been legalised. Domestic violence was something that was being talked about more openly. The pill had come onto the scene. All of these things were changing women’s experience and shifting the lens through which women, and that’s our regular characters as well as our guest characters, look at the world.

"So, it would be impossible, really, to make a drama about women in the 1950s and '60s that feels repetitive or would seem to turn in on itself because women are looking outward; women are questioning the world; women are arguing with the law; women are arguing with their husbands; and that in itself is very vital and very volatile.”

While abortion will have been legalised (with certain restrictions) in England under the Abortion Act of 1967 by the time we return to the streets of Poplar for season 12, from season 2’s graphic abortion scene in which an impoverished mother of eight turned to a backstreet provider, to season 8’s season-long arc about an illegal abortion provider maiming and killing the women of Poplar, Thomas has already deftly handled abortion, illegal abortion and the legalisation of abortion.

And it’s these storylines that remain the most memorable – and pertinent – for Thomas even as we reach season 12. “The abortion storylines always grab me by the heart and by the throat. And I find it shocking that they’ve become incredibly relevant. You know, particularly with recent events in America. So that will always be the standout strand for me, and it is a strand rather than an isolated episode.”

Read more Big RT Interviews:

• Dan Walker on his BBC replacement and what he's bringing to Channel 5
• Chris and Rosie Ramsey on 'riotous' new show and the future of their podcast
• Dolly Alderton: 'I didn't expect to sell so many copies - I wouldn’t have been so revealing'

As much as it is a show about women’s experiences, Call the Midwife is also a history of medical treatment in the UK, with storylines tackling spina bifida, tuberculosis and female genital mutilation also having been lauded over the years. But it’s the storyline concerning the thalidomide tragedy which Thomas is particularly proud to have told – and one she’s thrilled to be revisiting in season 12.

At the end of season 4, Stephen McGann’s Dr Patrick Turner prescribed thalidomide to pregnant patient Rhoda Mullucks (Liz White) as she suffered from morning sickness, whose daughter Susan was then born with birth defects in season 5 as a result.

Now, the show is revisiting the Mullucks family, with Rhoda set to have another baby in season 12, which Thomas reveals “puts them under a certain amount of pressure and gives them a lot to worry about". She adds: "We haven’t actually been with that family for five years, so we’re picking up the pieces for them and it makes for a very special Christmas special.”

Another emotive storyline in the Christmas special will follow a single mother as she's discharged from prison and searches for a community in Poplar. “And we also have a talent show, which has been enormous fun, honestly, both to write, rehearse and film. So there’s a lot of joy in there at Christmas as well.”

While season 12 will continue to tackle the thalidomide scandal, it will also chronicle medical advancements of the time and feature a ventouse birth for the first time. "Again, we’re looking at some very strong stories about the way society was changing at that time,” Thomas says.

Not all change we see will be positive, however. Season 12 will also be heavily influenced by Enoch Powell's inflammatory anti-immigration speech, which saw him dismissed from the Shadow Cabinet.

“In the very first episode of the new series, which will probably come out in January if it follows the usual pattern, I realised the timing of that episode coincided exactly with Enoch Powell’s Rivers of Blood speech which made a huge difference, and not a very positive difference to race relations in Great Britain.

"It was a big turning point for our society and the way we spoke of and behaved towards people who had come here from other countries, so that was something we felt we had to tackle.”

As for returning characters, Call the Midwife viewers can expect plenty of beloved old faces, as well as some new ones to shake things up. Fan-favourite character Trixie, whose presence has been sorely missed after actress Helen George left halfway through series 11 to facilitate George’s pregnancy, will be back with gusto.

"Something rather wonderful happens to Trixie, Lucile has to contend with a reasonable amount of sadness, and what else can I say? We have a new nun coming to join the line-up, Sister Veronica," Thomas teases.

Viewers can rest assured then, that Call the Midwife has plenty more stories to tell and, with a 13th season already confirmed for 2024, it looks like it will continue to be one of the smartest and most subtly subversive shows out there for years to come.

Read more:

• Call the Midwife star Laura Main thinks show is "close to the end"
• Call the Midwife set to bring back past characters "in a moving way"
• Call the Midwife's Helen George teases Trixie's "lovely" Christmas storyline
• Call the Midwife star reveals hopes for Nancy in season 12

Call The Midwife is available to stream on BBC iPlayer. Check out more of our Drama coverage or visit our TV Guide to see what's on tonight.

The latest issue of Radio Times magazine is on sale now – subscribe now and get the next 12 issues for only £1. For more from the biggest stars in TV, listen to the Radio Times podcast with Jane Garvey.