She died having sex with a horse! Royal's sex life on show
It's her third crack at playing a monarch, having already portrayed Queens Elizabeth I and II.
But for Dame Helen Mirren, perfecting her latest role, as 18th century Russian empress Catherine the Great, is something of a passion project.
The 74-year-old actor is furious at the way history has remembered Catherine, who was plagued with smears that she died trying to have sex with a horse.
Dame Helen said: "It's appalling the way history treats successful, powerful women. It has to pull them down. Her unbelievable achievements were very successful, obfuscated by history.
"I have feminist friends who say, 'Oh, what are you going to do about the horse?', which of course is a complete lie, a classic way of belittling her. She was in fact a serial monogamist."
German-born Catherine became ruler of Russia after deposing her husband, Emperor Peter III, a violent, drunken bully.
Despite being highly educated and cultured, she had many detractors, some of whom made up wild stories about her sex life to detract from her powerful leadership, all of which will play out on the series, which hits streaming on Foxtel in November.
And Dame Helen says the way Catherine has been portrayed over the years - compared with male monarchs - is a sign of misogyny that still exists.
She said: "You look at the way Louis XIV or Henry VIII behaved - their behaviour was completely acceptable, whereas Catherine had a series of four or five relationships, which in any modern woman's life is not that many.
"She certainly was never the sort of mad sexual voracious creature that history has made her out to be."
However, Catherine did openly have affairs with several men after her husband's death, and Dame Helen's new HBO/Sky Atlantic production Catherine The Great shows several saucy scenes in which she seduces her lovers.
One shows the Empress in the bath, while another has one lover climbing the stairs to her bedroom, only to be greeted by another lover heading down.
Dame Helen says to portray such a liberated woman was a pleasure - especially after playing Elizabeth I, the "Virgin Queen".
She said: "Catherine was completely open, there was no shame about it. I could not get my head around that, growing up with a post-Edwardian, post-Second World War, Protestant attitude towards sexuality - and having played Elizabeth I, about whom even the slightest whiff of a sexual relationship would have been the end of her.
"I found it extraordinary, but the attitudes towards sex in the 18th century were, in many ways, far more liberated even than they are now. I think we're still coming out of the Victorian age, in a way.
"Although the younger generation have a very different attitude compared to the world I grew up in. Female sexuality is far more accepted now.
"That has its drawbacks but in general I absolutely applaud that, I love it."
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Dame Helen, who was made a dame in 2003 for services to drama, also said she was delighted that it had become less taboo for older women to be seen having a healthy sex life on television.
In Catherine The Great, viewers are left in no doubt that the Empress was very active in the bedroom.
Talking about the way television has previously treated sex among the older generation, Dame Helen said: "If you did see it, it was something weird or unpleasant or to be laughed at or something.
"That's the way they put you down, you see. Women fighting for their rights are treated as if they're weird, as if they're funny, and that's how they crush you, how they stop you."
Catherine was a very serious leader, under whose rule Russia became one of Europe's great powers. She ruled from 1762 until she died in 1796, making her Russia's longest-ruling female leader. But in her private time she was frivolous and fun and loved to throw wild parties.
One scene in the series shows her Transvestite Ball, in which Dame Helen wears trousers and cravat, and Rory Kinnear - who plays her political mentor Nikita Ivanovich Panin - a gown, wig and rouge.
Dame Helen, whose own paternal grandfather, Colonel Pyotr Mironov, was in the Imperial Russian Army, said: "She loved the Transvestite Ball because she got to show off her great legs dressed as a man, while the men dressed as women.
"It was their version of a fancy dress party where they all laughed hysterically at each other and thought it was great fun. It was certainly a fun scene to film."
Catherine also loved to have romantic dinners for two with her lovers, who included Grigory Potemkin, a brave and handsome military leader.
The four-part series puts this affair at the centre of its story. Potemkin is thought to have been the love of her life, though she refused to marry him, as she did not want to relinquish any of her power.
Dame Helen said: "She was very romantic and she fell in love with people in this quite girly way. That was certainly one side of her character and her culture.
"Given the pressures of her professional life, I think she enjoyed her love life. She loved having these romantic soirees over a candlelit dinner and a great bottle of wine and falling in love again.
"That was her version of entertainment, her version of sitting down with the television and binge-watching Game Of Thrones. The relationship with Potemkin is interesting because he was the only one she really cared about. They fell madly in love, and it overwhelmed her physically and mentally and she was besotted with him.
"I think he genuinely loved her - but they were very much oil and water. They could never settle down comfortably together.
"He was always off on military expeditions in the name of the empire and expansion.
"Catherine and Potemkin knew they were going to have to live a lot of their life apart, so it progressed into a somewhat open relationship.
"Potemkin had many relationships with lots of women, but he never married anyone else. "There is a theory with some historians that they got married in secret and were in fact husband and wife."
Despite Catherine's lovers and the parties, Dame Helen prefers her to be remembered for her political intelligence and abilities.
She said: "She came in as a foreigner, took control, then maintained power - it was an incredible achievement."
This article originally appeared on The Sun and was reproduced with permission