Call the Midwife star offers update on next season - and reveals why she’s “never the lead”

Unlike her character in that, forensic pathologist Dr Wendy Newstone, Glen says she’s squeamish. “To research the part, all I did was read a wonderful book called Unnatural Causes by Richard Shepherd. He was one of the first pathologists on the scene after the Hungerford rampage and writes about it very movingly. But he has a way of putting on his professional hat that helped me in finding Wendy.

“I’d been in Silent Witness, but only as a victim and I was murdered very quickly! It was a wonderful job, though, as I got to lie down in an orchard all day. For Ridley, I made an audition tape using a mannequin lying on a table. I couldn’t believe I was offered the job.”

Glen had to get used to acting in scrubs, a hairnet and hood. “But Claire Lynch, the costume designer, let me be a bit more stylish in other scenes, with quite sophisticated clothes, glasses and ankle boots.”

Growing up in Helensburgh on the Clyde, Glen would make things and send them to Blue Peter. “Thanks to Biddy Baxter, I got all these precious little letters back and four Blue Peter badges.”

Years later, taking her portfolio to London after Glasgow School of Art, she got a job as a graphic designer at book publishers Thames & Hudson: “At my interview I said I could play alto sax and tap dance — they must have thought I was off the wall! Then after five years I danced off onto the stage.”

That career change was inspired by Alan Rickman. “I had joined the Questors Theatre doing production as a hobby, and one night he came along to critique the play. I’d never dreamt of acting, but he advised me to try it as he’d been a graphic designer himself and didn’t go into acting until his late 20s. I’ll always be grateful, as the next day I applied to drama school. I went to Bristol Old Vic at just the right age for the character parts I went on to play.

“For most of my career, I’ve done a day on this, a day on that. I’ve been very lucky, but I’ve often envied actors at the end of the day who are given the next call sheet! Waterloo Road was the first more regular part I did — it helps when a role becomes familiar. The terror I felt on the first day of The Crown [as Diana Spencer’s grandmother] was unimaginable!

”We’ll be filming the next series of Call the Midwife until November. I love costume drama because in a way it does half the job for you! They decided I needed some suits made for me at [costume suppliers] Angels in London. When something fits like a glove, it’s a game-changer. And if a costume is made for you, your name is sewn in. So when those suits are rented out in future, they’ll always be Miss Higgins’s.

“Heidi Thomas’s writing is what’s made the characters so popular. It’s rare to have women of a certain age on television — you’re usually the token oldie. Linda Bassett, who plays Nurse Crane, and I both enjoy the scenes we have together. Our characters are from very different backgrounds, but I think viewers relate to our friendship on screen.”

Perhaps surprisingly, Glen’s first experience of TV was in sketch shows with Harry Enfield and Paul Whitehouse. More recently she’s worked with Julia Davis and Daisy May Cooper. Besides comedy, what else does she like? “I’ve got hooked by Slow Horses,” she says, “and Dept Q. But I love Radio 4. I’ve done Radio Rep [as a voice actor] and it’s a wonderful medium.”

She is self-effacing about her own profession. “So much of what an actor does is just a tiny part of an enormous creative team, after months of prep and planning. You’re there to honour what’s gone before.”

Glen may never have been a lead, but the stars shine brighter for her quiet, quite brilliant support.

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