Image copyright ITV Image caption "There are lots of good crime stories on telly but Vera different," says Blethyn

TV viewer loyalty - the kind that propels a series into double digits - is these days a rarity.

Too many platforms offering too much content have us constantly tempted elsewhere.

Still, one show that's defied the odds is ITV's detective drama Vera, which this year reaches its decade-long milestone.

Admittedly, Vera began before the boom in streaming services. But its audience need not have stayed, averaging 7.8 million people per episode. It's also one of the best-selling British dramas internationally.

Our never-ending love affair with crime dramas could explain its longevity. As could the trend for those which are female-led. Yet the TV graveyard is populated with shows that can be similarly categorised.

Image copyright Getty Images Image caption Brenda Blethyn, director Mike Leigh and co-star Marianne Jean-Baptiste from Secrets and Lies

In truth, the secret to success lies in a fortuitous alchemy of ingredients.

Having Oscar-nominated Little Voice and Secrets and Lies actor Brenda Blethyn playing the eponymous sleuth is a good start.

Each stand-alone case episode is based on or inspired by the bestselling novels by Ann Cleeves, guaranteeing the source material is sound.

Her scruffy mac- and bucket hat-wearing Geordie detective chief inspector Vera Stanhope is a straight-talking, work-obsessed loner - with a compassionate underbelly.

In charge of a team of men (there is one woman), she has no time for the trappings of make-up, fashion, romance or personal angst. Solving a crime and seeing justice done are Vera's sole objectives.

Image copyright Getty Images Image caption Brenda Blethyn earned a best supporting actress Oscar nomination for Little Voice

Blethyn acknowledges Vera was initially a hard sell.

"I don't think people liked her very much," she says. "But then they could see she was respected by her team and she would defend them like a mother [dog] her puppies. So people began to warm to her," she says.

"There are lots of good crime stories on telly but she's different. She looks like someone who could live down the street. You don't know much about her personal life, you're not lusting after her, so nothing gets in the way of the drama.

"It's also good to see a woman of her age in a position of authority, telling a load of men what to do. I know lots of women around her age rejoice in that."

In person Blethyn is nothing like Vera. She laughs and cracks jokes and is glamorous in an understated way. You can't help but like her.

Image copyright ITV Image caption Kenny Doughty plays Vera's right-hand man Aiden

But she does share some of her characteristics - some born out of her humble background growing up in Ramsgate, she says.

"I'm a coper and can be pretty independent. And solving puzzles has been my passion from when I was a kid. We didn't have a TV and the radio would get cut off because the bill hadn't been paid. Still now, I challenge my brother every day to do the Times cryptic crossword."

Blethyn has built a strong friendship with Cleeves, has read all her books and feels very protective of the author's character. She will tell the scriptwriters if they've included something Vera just wouldn't say or do.

The show's executive producer Phil Hunter says Blethyn "embodies this character in a way which captivates an audience and really lands an emotional stone in the heart".

He also considers the show a "trailblazer" in female protagonist police shows.

"There's now an appetite for telling stories with really capable women in those positions. The more gender balance we get on screen, the better," he adds.

The new series' first episode sees Vera investigating the death of an entrepreneur whose body is found by bailiffs attempting to repossess his house.

Image copyright ITV Image caption Vera's trusty Landrover carries her around Northumberland

Ultimately, it is a classic "crime of passion" Vera story - one where the tension is ramped up, to be brought down to a cathartic conclusion.

Professor Charlotte Brunsdon from Warwick University's Department of Film and Television Studies says in this sense Vera "belongs more in the British detective fiction tradition, along with the likes of Inspector Morse and Rebus, rather than female-led detective series".

"Classic to that strand of detective fiction is that it sets a mystery that can be solved, shown in a real world, a flawed world. So you get the feeling of closure and satisfaction that Vera has managed to get something right," she says.

"But there's no pretence that she can put right the things that have caused either what's happened or the things she encounters along the way.

"In some ways it's misleading to think of her in relation to female detectives. Some of these shows tend to be more about the drama of being a modern woman.

"You get a lot about their private lives because they have endlessly to circle the question, 'How can a woman be doing this? What's wrong with her?' because it's still difficult plausibly to have female characters who are devoted to their jobs and aren't monsters."

It also means such series have a running narrative focusing on the woman's personal difficulties. Their stories have inevitably to reach a conclusion, meaning the show is more likely to fizzle out.

Image copyright ITV Image caption Vera uncovers a tangled web involving the dead man's business and family affairs

Among reviewers, the programme has its fans and detractors. The Telegraph's Michael Hogan declared after the first episode of series nine: "Brenda Blethyn deserves better than this slow drama.

"The script plodded from one plot point to the next, like Vera herself through the handsome Northumbrian scenery... This was Death in Paradise without the Caribbean sun or Midsomer Murders without the camp fun."

Meanwhile, Chitra Ramaswamy from The Guardian, praised the show, saying in 2016: "Brenda Blethyn stomps across the moor with a solvable murder on the horizon. What's not to like? Closely followed by Northumberland, Blethyn is the best thing about Vera...

"She has the loveliest voice, at once girlish and gruff. Her face is kind but means business. Not many actors can pull off shambolic but effective but Blethyn can do it with a single, penetrating glance from beneath that hat."

As the critics highlight, the setting of Vera is a key component. It's at once glorious and threatening - a character in its own right.

Image caption Brenda Blethyn: Not ready to hand up her mac yet

Vera has boosted tourism to the area, which was marked with a Royal Television Society Award last year. For each series the cast and crew spend six months filming all round Northumberland and specifically Newcastle.

As well as showcasing the beautiful landscapes, Vera delves into the industrial heartland. Kenny Doughty, who plays Vera's main sidekick Detective Sergeant Aiden Healy, loves the region.

"Northumberland and the coastline are breathtaking but people don't really know it's there," he says.

"And Newcastle has its own cultural identity. It's still rooted in its working-class roots and there's a real sense of community even though it's a city. I've never felt unwelcome. Everyone wants to talk to you, and everyone's got a story to tell."

If Ann Cleeves ever hangs up Vera's mac and hat, the TV scriptwriters could feasibly continue creating new stories way into the future. Contemplating getter older and older as Vera, Blethyn gets misty-eyed.

"Oh, imagine. It could be really good," she says. "But they would probably have to wheel me around in a chair.

"Deciding who would do it... well, they'd have to draw straws."

The tenth series of Vera begins on ITV1 at 20:00 GMT on Sunday 12 January.