Speculation is rife over Miranda Hart’s future in Call The Midwife after she announced a tour which will clash with filming of the fourth series.

The comedienne – who plays the popular character Chummy Noakes (nee Browne) in the show, will be on the road for large parts of next year – with dates set to clash with filming.

And a source told the Mirror that it could affect her future on the show beyond the third series, which is due to begin filming later in 2013

“She’ll be fine for filming this year but there is a huge question mark hanging over anything beyond that,” the insider said.

“Next year is all about the stand-up tour.”

Show boss Hugh Warren told the paper that the 50s set show – focusing on a group of midwives in East London – could change its line-up as it progresses, and that some characters could even face being killed off in the future.

“You could lose a few people – as would have happened in the real Nonnatus House, people would have come and gone,” he said.

“A death is always good – dramatically. There will be a turnover of both nuns and nurses.”

Call The Midwife – based on the memoirs of former midwife Jennifer Worth is one of the BBC’s biggest hits in years, with the current series, screening on Sunday evenings, pulling in audiences around the 9m mark.

Miranda, whose self-titled sitcom recently ended its latest series, won a National TV Award last month for her role as Chummy.