Screenwriter Sally Wainwright has high hopes for new drama

The screenwriter behind Last Tango In Halifax and To Walk Invisible is writing Shibden Hall, an eight-episode BBC drama about diarist Anne Lister.

Arriving at the South Bank Sky Arts Awards in London, Wainwright said it has been a mammoth undertaking.

She told the Press Association: “It’s been extraordinary. I normally allow a month to write a script and at the moment I’m averaging two months for one script because I’m having to read the diary in the original before I write the scripts and a lot of it is in code.

“I can read the code and it’s not that complicated, it’s what is called simple substitution cipher, so once you’ve got the hang of it, it’s not difficult, but I’ve got to transcribe the code, transcribe the plain hand and turn that into drama.

“It’s really good fun and really rewarding and I hope we are going to produce something extraordinary as a result, something unlike any other period drama for that very reason.”

Sarah Lancashire as Catherine in Happy Valley (BBC/PA)

She added: “Anne Lister’s diary is four million words long, I’m not using it all, I’m writing about her from 1832 onwards, but my only previous experience of period drama based on true lives I’ve had is To Walk Invisible (about the Brontes) so this is something new.

“I’ve been working on it for nearly 20 years, it’s been in there a long time and hopefully that is good, hopefully I’m lucky it didn’t get commissioned sooner, hopefully it’s lucky I have had that time.”

The long writing period on Shibden Hall means Happy Valley fans won’t see a third series of the police drama for some time.

Wainwright said: “It’s not been delayed but it will feel like a delay to the audience.

“But we always talked about there being dramatic value in there being a gap between the second series and the third for reasons that will become apparent in the narrative when you see it.”