Keira Knightley walks in the slippers of an 18th-century celebrity in The Duchess.

Paramount Vantage / Nick Wall

Knowing the backstory to The Duchess, director Saul Dibb’s sumptuous look at the chaotic escapades surrounding romance among the royals in King George III’s late 18th-century England, gives a whole new meaning to the phrase “what goes around, comes around.”

The film revolves around the Duchess of Devonshire, who was born Georgianna Spencer and is an ancestor of Diana Spencer. Entering marriage to a wealthy duke, she soon learned that he had a mistress on the side and only needed Georgianna to produce a male heir to his title. Her later attempts to find happiness in the arms of a man who had only love to offer, proved even more disastrous.

Two centuries later, Diana Spencer married Prince Charles to become the Princess of Wales and produced two heirs to the British throne while her husband kept Camilla Parker Bowles on the side. Diana later thrust herself into romances in the hopes of finding happiness, but we know where all that ended. What goes around, comes around.

As played by Keira Knightley, Georgianna is a great beauty who was one of the leading celebrity lights of her day. Other women fawned over her, trying to emulate her style in the latest fashions. Her lavish parties were where anyone who was anyone wanted to be. A woman of uncommon intelligence and wit at a time when women were thrust in the background, Georgianna was outspoken about politics, influencing the Whig party and being much in demand by politicians who wanted her to speak before the crowds to drum up support.

But her home life was very much in contrast. “Sold off” by her social-climbing mother (Charlotte Rampling) in marriage to the Duke of Devonshire (Ralph Fiennes), it at first seemed a joyous match for her with a bright future in his castle-like estate. But Georgianna soon discovers the duke is a cold fish who is only interested in her for the male heir he wants her to produce to inherit his title. Unfulfilled in their pleasureless romantic flings and complaining that there is little communication between them, she’s unhappy to find that he only views their relationship as a duty.

He’s actually in love with Lady Elizabeth Foster, known as Bess. She is his mistress and has given him bastard children. Eventually, the duke moves Bess (Hayley Atwell) into the manse where her presence, needless to say, causes friction with Georgianna.

To save her sanity, Georgianna seeks comfort in the arms of a childhood friend, the fast-track politician Charles Grey (Dominic Cooper). He sweeps her off her feet, although she realizes that such an affair is doomed by the conventions of the day. Although the reign of King George III was known as the Age of Enlightenment, it also was a time when women had few rights and could only secure a bright future by marrying into wealth.

The bittersweet The Duchess underscores the plight of Georgianna and, even without the Princess Diana parallels, is a fascinating behind-the-stairs look at a part of history that has been swept under the rug. Of course, those parallels make this story all the more relevant and current. Times may change, but the human comedy rolls on.

Dibb, who wrote the screenplay with Jeffrey Hatcher and Anders Thomas Jensen based on the award-winning biography by Amanda Foreman, has kept the action moving as it bounds along so we can see how a woman “who was brought up to please others” tries to make her own mark in the world. She does it with vivaciousness and style. But in the end, as the duke says, “Why would I make deals? I’m in charge of it all.”

Fiennes plays the duke as a remote, self-absorbed man who makes Georgianna’s problems all the more frustrating. Nevertheless, he demonstrates some compassion and is much more human around Bess, who is played by Atwell with a cautious understanding of the woman’s walk-on-eggshells station.

Cooper is all dash and loving sensitivity, despite an unfortunate wig. When it’s off, he’s much more handsome. But he’s something of a caged tiger who can’t get too close. When he does, it awakens in Georgianna a realization of what she’s missing in her own marriage and she blossoms.

Waiting in the wings, however, is the duke who warns her that he has the power “to make it all disappear” for her, even taking her children away from her and wrecking what had looked like a promising future for Charles Grey. It’s that threat, that things could collapse at any moment for Georgianna, that colors her character, makes her fear for her future and her sanity, even as she dares to enter uncharted territory.

It makes for edginess in a film that on the surface may seem like just an elaborate costume drama. Rather than mere costumes and pretty houses, the nice thing about The Duchess is that it makes these historical figures real people that one can care about because they turn out to be very much like us.

****The Duchess

Starring: Keira Knightley, Ralph Fiennes, Dominic Cooper, Hayley Atwell, Dominic Cooper.

Rated: PG-13, contains adult themes, sexual situations.

mjanuson@projo.com