Scarlett's star is rising - in her tattoo and on screen

Arriving at the royal premiere of her film about the marriage-loving monarch in London last night, Scarlett Johansson showed off a somewhat unregal tattoo.

The circular design on the Hollywood actress's left forearm shows a sun setting on the sea with a star in the sky.

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The tattoo, which Miss Johansson has had for over a year but has been kept under wraps, is unlikely to feature heavily in The Other Boleyn Girl, in which she and Natalie Portman, 26, play sisters Anne and Mary Boleyn, who battle to win the affections of Henry VIII.

Last night both actresses braved a chilled London evening ahead of the world's first showing of the period drama which was attended by Prince Charles and Camilla Parker Bowles.

Johansson told reporters she was impressed by fans, some of whom had waited for three hours for a glance of the stars on the red carpet.

She said: "Hopefully Charles will really enjoy himself.

"It's a really interesting story, it's very sexy and tumultuous and hopefully he will have a very good night like everybody else.

"Coming from New York the idea of having a monarchy blows me away so this has been a real thrill.

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"This is just another way to challenge myself and express myself as an actress.

"Natalie and I and Justin Chadwick, our director, took great care in making sure the project was not just a story about a love triangle and intrigue but a story about sisters and sisterly bonds."

Eric Bana, the Australian actor who plays a young Henry, said: "It was certainly a lot of fun and I was aided by a great script.

"You try and combine an bit of history and a bit of fantasy."

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He also joked that he would have a few words of advice for Prince Charles when he met him at the premiere.

The Chopper star added: "There are a few things I have learned about being king and I have got in there before him."

Johansson plays Mary Boleyn, the little-known sister of Anne who was rumoured to have given birth to Henry's child.

The movie features a strong supporting cast of British actors including Kristin Scott Thomas and David Morrissey.

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But its American stars' attempts at English accents have been much mocked by the critics.

Star Wars actress Portman said: "That was a big challenge. One of the biggest challenges, personally. It's a scary thing. I can't improvise with an accent at all."

Other celebrities at the Odeon in central London included Nancy Del'Olio, Lily Allen and Sophia Hyatt.