The new series of Call The Midwife had to be rewritten after Miranda Hart pulled out, its creator has said.
The actress, 44, who played loveable midwife Camilla "Chummy" Browne, announced last year that she would not return to the period drama despite suggestions from producers that she would.
Now, Call The Midwife's creator and writer Heidi Thomas has told Radio Times magazine that she had written Hart into the sixth series, which airs later this month, but that she withdrew at "relatively short notice".
"We were thrilled when Miranda approached us, and I storylined the series for her, but at relatively short notice she had to withdraw," Thomas said.
Asked how much notice she was given, Thomas said: "I can't say, but it was short. We were hopeful right up to the end that we could make it work, but we couldn't.
"I just rewrote the series without Miranda in it, which was sad because we would have loved having her in it. She is part of the Call The Midwife family. But (this time) it wasn't meant to be. "
Hart, who quit the show during series four because of work commitments, said that she could not return because she could not make the schedule work.
The new instalment of the BBC1 drama, originally based on the memoirs of Jennifer Worth, is set in 1962 and tackles the issue of female genital mutilation.
Thomas said that she ensured that a small detail, which the broadcaster wanted to remove on the grounds of taste and decency, remained on-screen.
Asked if she should have represented the issue more critically, she said: "We are a medical drama, not a moral drama. We are not judging this woman."
But she added: "There is one small medical detail on screen which the BBC did question, in terms of taste and decency. And we said very firmly if you erase that small visual moment, it is underplaying the horror and the pain of the situation."
While movies based on other period dramas such as Downton Abbey are said to be in the works, Thomas said she was not interested in a big-screen spin-off, saying: "It has never been discussed."
She said that she had received "expressions of interest from very senior actresses" to appear in the TV drama because of its strong roles for women.
And she added of the secret to the show's success: "Gradual, persistent change. In some long-running shows there is a pressure to keep characters going on and on with new stories, but that does not replicate life. My mantra is, 'We are not a soap. We are a medical drama'."