Image caption Heidi Tidow (left) and Belinda O'Hooley (right) with Suranne Jones

For the last two months viewers have been gripped by Gentleman Jack, BBC One's drama about the eventful life of 19th Century landowner Anne Lister.

Written by Sally Wainwright, the series stars Suranne Jones as Lister, a wealthy industrialist from West Yorkshire who lived a secret life with her female lover.

More than five million people have tuned in each week to see the drama, which reaches its climax on Sunday.

One of those people is Oscar-winning director Danny Boyle, who recently said Jones should win "every [expletive] prize" going for her performance.

A second series has been commissioned, while Shibden Hall - the house near Halifax where Lister lived - has seen visitor numbers treble.

As well as stimulating interest in Lister herself, though, the drama has also given a boost to O'Hooley & Tidow - the female folk duo who sing the song that plays over the programme's end credits.

Image caption Jones previously won a Bafta for her role in Doctor Foster

The Huddersfield couple's jaunty composition actually predates the show, having first appeared on their 2012 album The Fragile.

"From the minute we started performing it it was our hit basically," says Heidi Tidow. "We've been singing it non-stop for seven years.

"A couple of years ago we did a show at Hebden Bridge and Sally Wainwright was at it," she continues.

"She was filming Happy Valley at the time and she came up to us in the interval and asked to use the song in a drama she was writing."

Wainwright herself says she knew the song "would bring something magical to the closing moments of each episode [and] have a powerful emotional effect on the audience."

"Gentleman Jack" was the far from flattering nickname Lister acquired on account of her unconventional lifestyle and mannish attire.

A dedicated and prolific diarist, she detailed her liaisons in intricately coded entries that were only deciphered after her death in 1840.

Lister faced harassment and abuse during her lifetime, which the lyrics of O'Hooley & Tidow's song reflect.

"No one likes a Jack-the-lass," they sing of a woman who was "proud and stout and full of clout" and "played the fellas at their game".

One could say the same of O'Hooley & Tidow, who have managed to plough their own distinctive furrow through the traditional folk world.

"The fact we use a piano initially raised a few eyebrows, so we were breaking the rules from day one," says Belinda O'Hooley, who has been performing with wife Heidi since 2009.

"Also the fact we're visibly a gay couple sets us apart a little bit."

Image caption Sophie Rundle (right) plays Ann Walker, Anne Lister's lover

"In terms of music we often say 'what would Anne Lister do?'" continues Belinda, who was formerly a member of Rachel Unthank's Winterset group.

"Anne was fearless, held strong her beliefs and carried things forward with her head held high. We find that so inspirational."

Other women who have inspired the duo include Beryl Burton, the amateur Yorkshire cyclist whose life they honour in Beryl.

Another song, The Pixie, tells of Daisy Daking, a young teacher who taught Morris Dancing to soldiers during World War One.

Woman In Space, meanwhile, pays homage to Valentina Tereshkova, the Russian cosmonaut who was the first woman to travel into space in 1963.

"We've always been drawn to ordinary women doing extraordinary things," says Heidi, who is currently expecting a baby boy.

"These incredible women have done these incredible things completely under the radar and we've been captivated by their stories."

Heidi concedes there is "a certain amount of social conscience" to the duo's music but insists they are "political with a small p".

"We're not singing about party politics, like Billy Bragg and Grace Petrie," she says. "We're writing about what we're interested in."

Media playback is unsupported on your device Media caption Intimacy director advises BBC drama about shooting sex scenes

Having operated under the radar themselves for the past 10 years, O'Hooley & Tidow admit to being "blown away" by the interest their Gentleman Jack track has generated.

"There's been an avalanche of Spotify listens and YouTube hits, and our little shop on our website has basically broken down," says Belinda.

The couple have had to arrange more live dates to satisfy demand and are now fielding offers to perform in Australia, America and mainland Europe.

"I guess we're going to have to get our passports renewed," chuckles Belinda, who has a tattoo of Lister etched on her wrist.

"We're going to take one of Anne Lister's big leaps and see where we land."

Gentleman Jack concludes on BBC One on 7 July at 21:00 BST.

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