Actress Laura Main is swapping Shelagh's prim twinsets for dirty raggedy dresses – and the cosy dining room of Nonnatus House for the grim workers cottages of Quarry Bank Mill.
You'd think the two roles would be poles apart, but you'd be surprised at the similarities between Call the Midwife and Channel 4's gritty and grubby period drama...
"In many ways The Mill felt similar [to Call the Midwife] in that it is based in truth, and clearly there is great, great care taken over the authenticity of it all," Laura told RadioTimes.com. "It just felt like it was something else of worth."
"Yet it was going back further," she added. "It was going another hundred and twenty years further. It's period drama, but it is different. And a very different character."
Main plays Rebecca Howlett, a southerner who's travelled to the Mill with her husband John [Mark Frost], father, nephew and three sons. And she's a character Main was eager to ensure wasn't too similar to Shelagh.
"To begin with I was mindful of being different because I have been playing predominantly one role for three series. Call the Midwife takes up half the year, so just to begin with you’re making sure you don’t have any Shelagh-isms in there!"
While Rebecca is a mother, like Shelagh became at the end of series three, their existences do differ. There definitely isn't a female support network on offer like there is in Nonnatus House.
"It was tough, they [the Howlett's] clearly had to leave [the South]. It’s a big period of change. They don’t know anybody, they’ve just sort of arrived, they’ve left all their friends behind... I’m this lone female all of a sudden. There are a lot of dining room scenes but I was the one providing the food and organising it all, so it’s a much more old fashioned, traditional female role."
And, unlike Call the Midwife's dining room scenes, there is no Victoria Sponge, and very little light relief from the daily grind.
"There's no cosiness," admits Main. "It is gritty. They’re both gritty but in quite different ways. They both reflect their time."
The Mill's time has moved on a bit from series one. As Esther Price [Kerrie Hayes] comes of age and leaves her days as an apprentice behind, in the background dramas concerned with slavery and race, working conditions, strikes and women's rights play out. And it's a context which without doubt affects Main's character Rebecca.
"She’s probably a bit darker [than Shelagh]. But I think we’re seeing a different side of her because of her circumstances. There’s just that kind of drive to look after her family and survive I think. It’s survival instincts because things are that difficult for them as a family. There’s more desperation."
Not that filming was all dark and dreary though...
"There clearly was a great camaraderie on set, [she says, as Hayes and Sasha Parkinson giggle loudly in the background] so I guess that the hardest thing is being a part of that but also then keeping sight on how tough things were for them."
So does being involved in The Mill mean there will be more period dramas in the pipeline for Main? Has she found her genre?
"Being involved in a series [Call the Midwife] that returns is fantastic – and it’s a great problem to have – but it does leave you with a window of time, so I was lucky to fill that window with another great drama...
"I’ve not intentionally gone out to get another period drama. We’ll just see what happens!"
The Mill series two starts on Sunday at 8:00pm on Channel 4