Well before the third instalment of Pirates of the Caribbean, every man and his pooch knew Johnny Depp had modelled his character, Captain Jack Sparrow, on the Rolling Stones' eternal guitarist, Keith Richards.

So it was no great surprise that Richards was invited to play Teague Sparrow, Captain Jack's dad, in the final film of the trilogy, At World's End.

As a fellow Brit on set one day, an apprehensive Keira Knightley approached Richards to introduce herself.

"Hello, I'm Keira," she said, holding out her hand.

Richards turned and eyed the beauty up and down.

"Gaaargh," he said.

And that was it.

"That's all he said to me," Knightley says.

Then she laughs, dissolving any Hollywood pretence.

As an A-list actor this might be Knightley's greatest achievement.

She hates Hollywood so much that not long ago she declared she was seriously considering quitting acting.

Knightley works at keeping her rough edges. She swears. And not politely, but like a brickie that has jammed his thumb.

"There's always a point," she says, talking about the size of the Pirates project, "when you say, 'Oh f---, this is enormous' ".

She is confrontational.

When the inevitable and interminably boring topic of size zero models and actors comes up -- Knightley has been thrown up as the poster child for the hungry generation -- she attacks the suggestions.

"How does it feel," she says to her interrogator, "if somebody should say you have a mental illness?"

Her continued link to anorexia, alongside the paparazzi constantly camped on her doorstep, has driven Knightley to believe she truly does want to give up acting and leave the lifestyle behind.

"At times it makes life difficult," she says. "I could hire people at huge expense (to keep people away), but . . ."

But, she finally admits, she's too frugal for that.

Plus, no matter how big and burly the bodyguards, how could they stop the constant eating-disorder innuendo?

So forthright is Knightley, when it comes up, once again, you almost feel sorry for the poor woman asking the question.

"That's a fascinating word, isn't it," she says. "Illness. Doesn't that say a lot?

"In your business, from what I can see, you have deadlines and there always has to be a drama every single week. Nobody can keep up.

"But I do not have an eating disorder. I have never had an eating disorder. It is pure fiction. It is a lie. It is slanderous.

"I have publicly denied it."

If there is anything that holds Knightley to her job, it is days like the time she was about to pose for the cover of Vanity Fair, when photographer Annie Liebovitz sprung a surprise by asking her and Scarlett Johansson to pose nude.

"It was one of those days when I hadn't shaved my legs and Annie went up and said 'Could you do it nude?'," she recalls. "And I went 'F--- it, all right then'."