Warning: contains some Yellowstone plot spoliers

Cowboys, murderous revenge plots and family secrets have kept Yellowstone fans hooked since 2018.

It is one of the most watched shows in the US and turned creator Taylor Sheridan into the king of prime time television.

But last year, Paramount announced that the fifth season, which is due to end next month, would be the last.

Its star, Kelly Reilly, tells me it will be “an ending to the Yellowstone world we have known”.

“Does it mean it’s the end of me playing her? Maybe, maybe not,” she says. “We don’t know yet is the honest answer.”

There have already been two Yellowstone spin-offs, with more in the works. Reilly, who plays the troubled and volatile Beth Dutton, says she would “love” to keep playing her character, but any spin-off “would be a new beginning somewhere”.

It sounds like something is possibly in the works, though, with Reilly saying she “can’t talk about the future because there are so many conversations happening”.

Yellowstone’s drama on screen has been mirrored off screen, with the departure of its leading man, Kevin Costner.

He only filmed half of season five because of what he says were contract and scheduling issues.

Sheridan has said it was down to Costner’s wish to focus on his Horizon film series, which the star is directing, co-writing, producing and starring in.

Either way, it leaves British-born Reilly as arguably the star of the show.

The daughter of a police officer and a hospital receptionist, the actress was born and brought up in Chessington, Greater London.

A far cry from the Hollywood Hills.

She has previously starred in True Detective, Prime Suspect and Above Suspicion.

But Yellowstone has introduced her to a huge international audience.

I ask how it feels to be an in-demand leading lady.

“Well, I’m 47 years old, it hasn’t happened overnight, you know. So it’s not like I’m getting whiplash,” she laughs.

“I have been a working actor for 30 years. It’s not lost on me that there’s a unicorn of shows that have such success worldwide and a character that has had this amount of attention or appeal.

“But I treat it at arm’s length. I don’t spend too much time thinking about it. I have a very normal life. It’s very important to me that my life is normal. Nothing has changed, other than I’m really busy.

“I don’t get to sleep at home very often, which is annoying because I love home!”

Most fans assume Reilly is herself an American, not the softly spoken Brit she is in reality.

She tells me that when Yellowstone started, she “didn’t do any press” because she wanted people to believe in her character.

“People talk to me as if Beth is real,” she says. “We all talk about Beth like she’s a real-life person.

“I’m always going to be a bit of a let down when people meet me. I go into the local bakery and the lady is like, ‘I’d love to drink with you.’

“I know what she means – she wants to drink with Beth. People want to feel part of that energy… someone so connected with their primal self.

“And we’re so disconnected. We’re all on our phones, on social media. It is like it doesn’t happen if someone doesn’t take a picture of it. Beth is the opposite of that. She is just so alive.”

To say Reilly’s character has been put through the wringer would be an understatement.

Beth has survived attempted rape, attempted murder, crushing heartbreak and being betrayed by family members.

She even exclaims: “I am the rock therapists break themselves against.”

Reilly describes Beth as a “powerhouse”, telling me it’s been “such a fun adventure to put her on”.

“I’m very introverted,” she adds. “I don’t have any dreams of vengeance in my life.

“There’s something really exciting about playing her. I feel like I’m on an adrenaline rush for four months while I play her, and when I’m finished I’m like, I now have to go back to my quiet, boring life. And I’m very grateful for my quiet, boring life after I’ve played her.

“But by the time every summer comes around where I’m sort of gearing up again and the scripts start coming in, I get excited again to meet her.

“I’m very aware of the gift of her as a character, but I lock her up in a padlocked box for six months of the year.”

The character of Beth quickly became a fan favourite, with articles devoted to getting her character’s look, and thousands of social media posts about her.

One of Beth’s most memorable lines of dialogues, “You are the trailer park, I am the tornado”, is even printed on T-shirts.

What does Reilly put that popularity down to?

“She’s unequivocally herself and unapologetic about that,” she says. “And as a woman, it is so refreshing and so much fun to play.”

The actress believes Beth “has penetrated a zeitgeist in women specifically”.

“I think it is that unencumbered kind of freedom that she moves through the world with. She is not afraid of dying, she is not afraid of losing.

“There is a scene in season two where she is being attacked by a man who is in the process of raping her and is about to kill her and she is covered in blood.

“She will not be a victim to him. And I think for women and for me, I love that. She is fierce.”

After all the trauma her character has experienced, Reilly says she “goes through different phases” of considering what a happy ending would be for Beth.

“I trust Taylor and his vision for her. He loves her so much,” she says.

“I would like something cathartic, potentially. I would hate to leave her out in the wilderness. But I don’t know if happiness is something any of these characters strive for.

“They strive to protect, they strive to kill, they strive to be killed. These are not looking for peaceful lives.”

Yellowstone season five part two is on Paramount from Sunday, 10 November.