First pictures of Nonnatus House newcomer Nancy as Megan Cusack joins Call the Midwife

Nancy, played by newcomer Megan Cusack, is "a trainee midwife from Ireland who comes to stay at Nonnatus House and learn from the rest of the midwives".

Plot details are being kept under wraps for now, but Cusak has described her audition process as "a whirlwind" that lasted less than a week.

"I got an audition through from my agent, I had a self-tape," she told RadioTimes.com and other press. "It was so quick-paced, I got it [the audition] on the Friday, filmed it on the Sunday, sent it off on the Monday, and then got the call on the Wednesday saying that I’d got it [the part]. So it was a bit mental. I was just there like – ahh! And then the next I was in getting hair and fittings and being measured. And then the week after, it started. So it was definitely a whirlwind."

Cusak admits that she felt "intimidate[d]" ahead of joining the rest of the cast on set, but soon realised her nerves were unfounded.

"It’s been 10 years, this is the 10th year [of Call the Midwife], it’s well-oiled. So it is – it was slightly intimidating, the thought of it, but then everyone – as soon as I got there, everyone was so welcoming, never once did I feel like I was a burden or slowed anything down. If I had any questions or didn’t know what was going on, people were very good to kind of be like, right well no don’t worry we’ll take the time, let’s sort this out."

On her character Nancy, she teased: "She’s a bit ditzy. She’s erratic, not great with her studies, but I think she’s very – she’s got a big heart, very warm, chat to everyone. Her chat doesn’t necessarily always make people feel good, she makes people nervous I think sometimes with how she talks. She doesn’t have a filter, which I quite like. She doesn’t think before she speaks, which I find really funny. So I enjoy that."

Call the Midwife continues on Sundays at 8pm on BBC One. While you're waiting, take a look at the rest of our Drama coverage, or check out our TV guide.