How very irreverent! They're Call The Midwife's saintly nuns, but Pam Ferris, Jenny Agutter and Judy Parfitt have a few confessions to make...

There they sit in their nuns’ habits and wimples looking as pure and innocent as a fresh sprinkling of snow. 

See no evil, hear no evil, speak no evil. Ha! Not these three. Call The Midwife’s Sister Julienne, Sister Evangelina and Sister Monica Joan may be Britain’s favourite TV nuns, but the actresses who play them? Well, they’re not quite as angelic as they appear.

‘What’s that you say?’ asks Pam Ferris, 66, who plays no-nonsense Sister Evangelina, putting her hand to her ear as she sits down after a morning’s filming. 

Sister Evangelina (Pam Ferris), Sister Monica Joan (Judy Parfitt), Sister Julienne (Jenny Agutter) on the set of BBC'S Call the Midwife 

‘I’m wearing the great British burqa – your jaw doesn’t open properly and you can’t hear anything in these wimples. It may be a form of penance for a nun, but it’s hard for an actor.’

Judy Parfitt, who plays the wonderfully batty Sister Monica Joan in the drama about nuns and midwives in early 60s east London adds grumpily, ‘And it’s so hot in this outfit.’ Jenny Agutter, perfectly cast as beatific Sister Julienne, giggles, ‘We’re very good at moaning together, as you can see.’ Pam cackles, ‘Oh yes, we’re very good at that.’

All three of them, however, appreciate just how lucky they are to have these jobs; the fourth series of the show has been as popular as ever with regular ratings of more than 9 million. 

‘I tell the young people on set to make the most of its success because this sort of thing doesn’t happen to most people in this business,’ says Judy, serious for a moment. ‘To get a show that’s so humongously successful and adored is rare. 

I think it’s because it portrays a different way of life; people had faith back then and they looked after each other. Life has become splintered now; religion has gone down the drain.’ Jenny, 62, agrees about the show’s appeal. ‘It isn’t so much about religion but about faith. Through these characters you understand real tolerance and the idea of a community and families working together.’

Sister Evangelina and Sister Monica Joan's face off in the kitchen

And so what was meant to be a chat about Britain’s most popular drama turns into a debate about faith between its three veteran actresses. ‘I have to tell you I’m an atheist,’ says Pam, interrupting Jenny. ‘I can’t let this conversation go on about how wonderful faith is. I don’t even know what faith is; somebody has to define it for me before I can discuss it.’

Judy, 79, sighs, ‘Faith is something that’s been created to help people get through life. Jenny and I were both taught by nuns at convent schools; I’m a lapsed Catholic. Nowadays people send rockets into space and I think it does make you question if there’s a God. They can make babies in a dish now! Everything we’re seeing goes against what people always believed in.’

Jenny Agutter, who was educated in convents during her peripatetic childhood in an Army family and whose mother was a devout Catholic, clearly believes in the power of faith and religion more than her friends, even though she’s lapsed. 

‘With progress you just have to care more. I think we’ve lost the sense of how communities work together.’ But Judy disagrees. ‘I’m against organised religion of any kind. It’s hard to have faith when you see what’s going on in the world in the name of it; look at what’s happening in Syria. How can people like Isis go around killing people and say, “This is in the name of God”? It’s a joke – but they totally believe it.’

Both Jenny and Judy (pictured) were taught by nuns themselves while in school

Jenny butts in. ‘There have always been wars about faith.’ Pam crosses her arms and enters the fray. ‘People say, “Don’t destroy my illusions” but I think it would be better if our illusions were destroyed. I have enough trouble dealing with reality as I see it without having to pretend there’s another layer.’ 

It must be tough playing a nun then. Pam sits back and sighs. ‘No, I don’t have to be a murderer to play a murderer. I am interested in religion, and as a person without faith I can observe it in a freer, more objective way and I think it helps me play Evangelina. I love her, she’s magnificent. She became a professional medic when women were struggling to get any medical training at all.’

In this series Pam has been able to explore her character more, and she particularly enjoyed the challenge when Sister Evangelina thought she was seriously ill. ‘She was really, really frightened,’ says Pam. 

‘She felt her mortality was at stake. We’re all afraid, however much faith we do or don’t have, when it comes to the prospect of a terminal illness. She was also beginning to feel her purpose in life had been blocked; how do you believe in a God that calls you to do things but then makes you so ill you can’t do them? The illness was very frightening to play. You draw from your own experiences. I’ve had scares; mercifully nothing has ever materialised but most people my age do have scares and it’s terrifying. I think Evangelina’s faith does help her with that.’

All the sisters have had meaty story-lines in this series; a few weeks ago we discovered why Sister Julienne chose life as a nun when a former boyfriend, who she left to enter the church, made an appearance. 

‘Although I’ve met the niece of the real nun Julienne was based on, I’ve always struggled to understand where the faith came from and why she went into the church,’ says Jenny. 

‘So it was good to get a bit of back story, to discover something new about her life history which means I have an extra understanding of her character. I love her but I don’t always understand her; her absolute tolerance. I think if I was in her position I’d want to change the circumstances around me but she accepts them and deals with them.’

Meanwhile, for Judy, playing a woman who suffers from a form of dementia is always a challenge. ‘She’s so multi-coloured and unpredictable,’ says Judy. ‘It’s not an easy ride because she’s complex and that’s why I love her and like doing it. She’s very broad-minded and not judgemental like the young ones. She often says there’s nothing wrong with being different. She likes to muddy the waters too, in a mischievous way.’

Although Jessica Raine, who played Jenny Lee, the real midwife whose memoirs the books are based on, is no longer with the show, all three actresses believe that in some ways this series is the best yet. 

It’s already covered some of the biggest issues of the time including homosexuality, syphilis, prostitution and child neglect, while for its characters there have been broken engagements, new romances and the return of midwife Cynthia who’s become a nun. ‘In terms of stories it’s really strong,’ says Judy. The other two nod their draped heads. At last, there’s something they agree on!

Call The Midwife, tomorrow, 8pm, BBC1.