Call the Midwife’s Stephen McGann: If I annoy my wife Heidi Thomas you never know what could happen to Dr Turner!

The actor stars as Poplar's dedicated and diligent GP Dr Turner in the BBC1 drama and is also married to the show's creator and screenwriter. But while he never begs her for particular storylines, he's on his best behaviour when Thomas is deciding on his storylines for the next series.

"If I'm not careful if I have a row with her, you never know what will happen," he tells RadioTimes.com. "Or what terrible disease would be fall me.

"But the only one time she - this is true, straight up. She's in this phase at the moment where she storylines, so that's the most interesting phase, and she's at her most quiet. You never, ever hear - we've always kept a real separation between the two.

"But just one year a few years ago, she was at the breakfast table with me. There I am with my cereal. And she said, 'How would you feel about losing a lung?' And I went, 'WHAT?! What have I said, what have I done?' And she said, 'Oh no no no, it's just an idea.' It never came to pass, thank the lord, but it was just one of those things."

He jokes: "You obviously can tell when she's thinking of stuff, so I try not to offend her at this time. You don't know where it will lead."

Call the Midwife is one of the most heartwarming shows on television, but it has also gained a reputation as a tearjerker which has covered serious emotional and medical topics - from alcoholism to domestic abuse to thalidomide poisoning. And McGann is convinced this makes the show ever more important.

"It's absolutely vital," he says. "I think everybody across the world who watches it, and many people do – that seems to resonate with them more than ever at the moment.

"Now the trick is not mine. It belongs to that lady over there who writes the show. It's a brilliant trick, I don't know how she does it and I've been married to her for years. But to mix lightness with poignancy, with sometimes really dark stuff to take you to dark places is a very particular skill.

"People go on a ride with us. And they do know that sometimes it won't always end up somewhere nice, but because of the balance we bring, they know - there's a few words that keep coming through this year, which is sincerity and kindness. Now in drama you can be sincere and kind. Whoever said you couldn't be - why does everything have to be darkness and dead bodies? Why does everything have to do that? Life isn't always like that.

"I would suggest - politely - that there is slightly more kindness and generosity than dead bodies lying around in everybody's life. So actually it mirrors real life a bit more. People are these things as well, and when you mix the dark, the light, the sad times with also something that can give you something to carry on the next day with. I think that says an important thing about the way we all really live."

Call the Midwife airs on Sundays at 8pm on BBC1