Nurse Val actress Jennifer Kirby: Call the Midwife's characters are never defined by men

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"But all the characters in Call the Midwife are defined by, first and foremost, their professionalism, and what they do as their job, and how good they are at what they do, and that they're quick-thinking and dynamic and powerful.

"And I think that the world needs a little bit more of that. It needs to be shown a little bit more on TV. Because women are brilliant."

The BBC1 drama is based on the memoirs of real-life midwife Jennifer Worth, and adapted by Heidi Thomas – whose other adaptations include Little Women, Cranford and I Capture the Castle.

Call the Midwife is now in its seventh series and attracts many millions of viewers each Sunday night, yet is still sometimes dismissed as fluffy and lightweight. Kirby says she isn't irritated by the misconceptions, however.

"It doesn't annoy me, but I always encourage people to watch the show because anybody who watches it realises very quickly that that's not what it's about," says Kirby.

"It is very warm, and very heartwarming and caring, and it's about love. But it's also quite dynamic and pushes boundaries and it's always looking and striving to do new and different things."

Heartwarming as it is, the show also has a more serious side, exploring topics from stillbirth to thalidomide poisoning to post-natal depression.

"I think that's very important and I think that's one thing that the show gets perfectly right, is the perfect balance between the warmth and between the harder and sadder moments," Kirby says.

"It's like life, isn't it? We all have very bad moments but also wonderful moments as well."

Call the Midwife airs on Sundays at 8pm on BBC1