Olivia Williams (top) confesses that she never watched Downton Abbey. Now she’s starring in what might be called a darker-toned sequel.

The Halcyon, an eight-episode series set in London just as World War II erupts, gets its American debut Monday at 10 p.m. ET on Ovation.

Williams plays his wife Priscilla, properly addressed as Lady Hamilton. She unexpectedly finds herself in charge of the hotel, whose nuts-and-bolts operations have long been handled by the ambitious and sometimes oily but skilled Richard Garland (Steven Mackintosh, right).

Lady Hamilton doesn’t much like Garland. Then, as we meet her, she doesn’t seem to like much of anyone. This has something to do with walking in on Lord Hamilton engaging in a little of the old slap-and-tickle with a younger woman – an encounter the hotel staff tried to keep Lady Hamilton from discovering.

“When a woman is called a bitch, you try to think why she’s behaving like that,” says Williams. “In this case, she has a really good excuse.

“I’ve been in that position myself, being the only one in the room who didn’t know that my supposed love was f---ing someone else.

“When people are being humiliated, they may react.”

As this suggests, The Halcyon has some strong and unvarnished character development, including and not limited to Lady Hamilton.

“She’s a victim of her time and her class,” says Williams. “She never really had a chance. She’s socially isolated.”

Her life was largely proscribed from birth. She would marry into her proper class, then provide children and dutiful support to her important husband.

As The Halcyon moves forward, however, so does Lady Hamilton. “British society is built on smiling and carrying on,” says Williams. “She discovers a whole new life, and someone later finds her soft spot, in both the literal and metaphysical sense.”

There’s a tacit connection here to Downton Abbey, in the sense that all the female characters gradually took bolder steps than their grandmothers were permitted.

That’s not ancient history. The 49-year-old Williams notes her own grandmother was boxed in by societal expectations.  

“She was a painter, a graphic designer,” says Williams. “But she never got a chance to fully develop that, because she had only a tiny window of time between leaving home and getting married.”

Real-life society, Williams adds, still hasn’t completely broken down those boxes.  

“You see things happening now not just with women,” she says, “but with gay people, refugees, black people and others. We keep waiting.”

On the historic side, Williams notes that The Halcyon illustrates an important evolution for the Downton Abbey class of aristocrats. World War II accelerated their move away from the ancient grand estates.

“During the war, much of the upper class couldn’t afford to keep up the estates,” says Williams, “particularly with much of the help off fighting the war. So they moved into the city, to homes there or to a hotel.”

The hotel option turns out to provide a perfect dramatic framework for The Halcyon.

“Setting it in a hotel is a wonderful thing,” says Williams. “There’s a constant turnover of people you might not meet in the isolated life in the country.

“For Lady Hamilton, you see how pressured she is, but it brings out her skills.”

The hotel’s role as a cultural center of wartime London also enables The Halcyon to dramatize something indomitable about the human spirit.

“Outside at night during the blackout, you couldn’t see anything,” Williams says. “I remember my grandfather saying he was going home one night and walked into a lamppost.

“But when you went into a hotel like the Halcyon, it was bright and glittery and glowing. My husband’s grandmother was a big dancer. She’d get the train from Norfolk to the city and go to ballrooms where she would dance with the black American GIs. Then they’d talk together.

“It’s that determination to be alive when death is so near.”

Lady Hamilton finds some of that determination herself, though it stems from different bad specters.

The first is Lord Hamilton’s (right) betrayal, the impact of which Williams says “any woman can understand.”

The second is finding herself on her own.

“When you’re married for so many years,” she says, “even if it’s not a good marriage, then you find yourself suddenly alone, I can’t think of any other life change that could be that drastic.

“It can be an opportunity, but it takes a terribly long time to see it that way. It’s a challenge.”

All this may explain some of Lady Hamilton’s attitude, and if her sharp tongue isn’t always welcome to her fellow characters, Williams says it makes her a delight to play.

“God bless television,” she says. “If you’re not a superhero and in your twenties, the movies only want you as someone’s mother or grandmother.

“It seems like TV executives believe a show can be carried by a middle-aged woman.”

Williams’s own recent TV shows have included Dollhouse and Manhattan, which she wishes could have continued through “its real ending,” the dropping of the first atomic bomb.

After playing characters over the years from Jane Austen to Eleanor Roosevelt, she calls it “an amazing run” and adds now is “a good time to be 49 years old.”

For the record, she also doesn’t see Lady Hamilton as just a b-word.

“Nobody thinks they’re a bad person,” says Williams. “Someone who played Iago said that. I can defend my character to the end of the Earth.”