Ruthless mistress for randy Charles

Helen McCrory wipes off her make-up as we chat about royal bed-chambers.

We're on location in a castle courtyard at Lednice in Moravia, where the actress has been filming scenes for Charles II: The Power & The Passion.

She portrays the vivacious Barbara Villiers, Lady Castlemaine, who enjoyed many merry romps with Charles before and during his reign, and bore him several children.

When McCrory first meets Rufus Sewell's Charles she sweeps forward to curtsy, her bosom heaving in a red velvet gown, inclines her head, and gently brushes his breeches with her nose.

'She's a predator,' Ms McCrory agrees.

One historian described Lady Castlemaine as a 'magnificant creature' and Ms McCrory has brought her to life with brilliant visual flourishes that give you an absolute sense of who this woman was.

'She's like an animal. You admire her because she's so carnal and ruthless - but you also loathe her because she doesn't appeal to any of the higher points of humanity, like trust or faith or love or hope.

'She has none of it - she has to be a realist and pragmatist.'

Within moments of meeting Charles (after ditching her husband, Lord Palmer), she has him in bed.

McCrory has a commanding presence. She walks into the monarch's chambers, shouts 'Get Out!' to the courtiers attending Charles, and lets a beautiful cape fall to the floor. The nudity is brief, but the effect electric.

In fact, director Joe Wright films such moments with lustful, yet tasteful, passion. It's not the kind of vulgar bonking we've seen in many costume dramas.

Lady Castlemaine is, of course, one of several women in Charles's life. They include Shirley Henderson as his wife Catharine of Braganza, Emma Pierson as Nell Gwynn, Melanie Thierry as Louise de Keroualle and Alice Patten as Lady Frances Stewart - who spurned the regal overtures.

Castlemaine used her sexuality as a means of survival. 'Barbara was a very ruthless and ambitious woman who really has no alternative but to use her sexuality and her intellect because she has nothing else to bargain with,' McCrory says. 'I've had bedsores filming this part.

There are a lot of bedroom scenes,' she jokes as she lists men she sleeps with. 'There's Charles, his son, my cousin - not to mention Churchill, who I pay £500 to spend the night with!