Laura Main has said she thought the end of Call The Midwife series three felt so wrapped up that she has been wondering if viewers think it’s all over.

Laura plays Sister Bernadette in the BBC period drama and reveals it had been a big upheaval for key character Jenny Lee (Jessica Raine) to leave at the end of the last series.

“I wonder if people will think there isn’t a fourth series because it felt so final in so many ways – so many stories were tied up. But Jennifer kept in touch with the nuns for the rest of her life, particularly Cynthia.

“Before now, I couldn’t see how it would work, but I think the show has expanded so much and we’ve got to know all the characters and the world they inhabit so much better now over these three series that I think it’ll be more than fine.”

Laura added that she was missing Jessica: “I have seen her recently and I let her know I missed her. The first scene around the dining table was also one without a couple of other characters, so you get used to it. And really fantastic actresses have come on board.”

In the fourth series Vanessa Redgrave, who has been the narrator since the beginning as an older version of Jenny, appears on screen for the first time.

“That’s really exciting,” says Laura. “Mature Jennifer will be on screen for the very first time. I was really quite moved when I saw that on the page.

“It’s a new dimension and quite poignant really to see Jennifer Worth [whose memoirs the show is based on] – this is her as she was when she was writing her memoirs.”

Call The Midwife will return to BBC1 at Christmas with a special episode; series four will air in 2015.