For men of a certain age, the name Jenny Agutter conjures up unforgettable images of an English rose swimming with not much on (think Logan's Run, Walkabout). Could Sister Julienne of Call the Midwife be tempted into such aquatic nudity, perhaps a birthing pool scene, in series two?
Agutter sounds bemused by the prospect: "I think we'd have to get to the seventies to do that... it'd have to run a hell of a long time, but it's a lovely thought. But it's quite a long journey from the scantily-clad Jessica and the girl swimming in the pool to a nun with a wimple, I must say."
It may well run that long. Call the Midwife has found such a favourable reception with Sunday night TV audiences that it's trounced even Downton in the ratings and had a second series commissioned barely before kicking off the first. So why's it found such a niche?
Agutter was initially equally perplexed:
"Someone in the supermarket told me how much she loved it, and I replied, 'Could I ask you why?'," she remembers. The lady told her it was a refreshing change to see characters so unusual from the usual telly fare, something with which Agutter heartily agrees.
"From Jennifer Worth's memoir, all these interesting people occur, and they’re quite eccentric. People are looking at a 1950s that they never normally see, and they're hugely different from the 1960s. So some people feel nostalgic, while others get caught up in the wonder of childbirth. Birth always represents hope and redemption, and here it's set against lives that are obviously completely disastrous.
"These characters are picking up the pieces after a very difficult time, and there's so much generosity of spirit, because they have been through so much. Everyone's just relieved to have the war over, to be building something new, so they're happy to do it..."
The second series may have put paid to a few holidays this year for Agutter and her husband, but she's delighted to be gearing up for a second run, with hopefully a bit more outdoor action for Sister Julienne:
"I love the relationship between her and Jenny, so there's more dynamic there for us can play with, and it'd be nice to see her get out and do the job, she's been stuck in the house for a while. I'd like to get on my bike and out there with my bag."
Surprisingly, despite having a much-loved son, Agutter doesn't claim to share the maternal instincts of Julienne:
"I love the character, but it’s not me at all. When I had my son, I never felt an instinct as to what motherhood was about - it all seemed peculiar to me, perhaps because I was 37. Everything about your life is completely out of control, I'm not like Sister Julienne who is accepting and has instincts about humanity, although I can admire it. Nursing I can understand, although I wouldn't make a good nurse either. I'm empathetic, not sympathetic. Trying to take a splinter out for someone would be awful, I'd be squealing.
"I had the pleasure of meeting the niece of Sister Jocelyn on whom Julienne is based - and she'd kept all her aunt's artwork and lots of letters - she used to write to everyone, including a few times to Maggie Thatcher.
"She told me about her characteristics, and it clued me in as to what kind of person she actually was, and in a way where that absolute faith comes from, which is the hardest part."
Agutter was famously a child actress - appearing to timeless effect as Roberta in The Railway Children - before really learning her craft, she says, at the knee of such luminaries as Sirs John Gielgud and Peter Hall at the National Theatre - "I didn't even know what an iambic pentameter was, until Gielgud taught me," she remembers admiringly.
"But this industry is extraordinary," she continues. "If you paint or write, you're not in any category. I still feel 25, but I've got to an age where I've got to think about old woman roles, and look around for them. So when you get something like this, it's fantastic."
And, to this day, do people still stop her to ask her about The Railway Children?
"Oh, yes," she explains patiently. "It's shown all the time, so it stays very present. Fortunately, it's not something I feel horrified by, and I've grown up in other roles, so it never got in the way of casting. Some people did get upset when I played the mother in the TV version, they thought I had to be Roberta, so I had to point out to them that time does go by."
Call The Midwife is released on DVD on Monday 12 March. Here are some pictures from everyone's favourite Sunday evening nostalgia trip: