To audiences around the world, Emma Thompson is that very English character actress who tends to pop up as the sensible one in costume dramas such as Sense and Sensibility or big-budget Hollywood productions such as Nanny McPhee.
But her latest theatrical foray is a far cry from roles such as Miss Kenton in The Remains of the Day. It centres on the horror and abuse of the international sex trade.
The Oscar-winning actress will return to the Edinburgh Fringe – where she started her career – later this year as executive producer of Fair Trade, a play based on verbatim accounts of prostitutes tricked into coming to London. It will be staged by the tiny Shatterbox Theatre Company. She became involved after meeting the show's writers, Anna Holbeck and Shelley Davenport, through the human rights group the Helen Bamber Foundation.
"So many people think they just come here to make money, that they're just on the make, and it couldn't be more different," she said. "Sex trafficking is a hugely important subject, and I believe we need as much art as we can get to help people understand what's going on."
Thompson, 51, is a patron of the Refugee Council and has spent many years campaigning for immigrants' rights – she has informally adopted a 16-year-old Rwandan refugee and successfully fought against his deportation. She also works with the Helen Bamber Foundation, which provides support to survivors of torture.
"It's all the little efforts that produce a shift in consciousness," she said. "And what's more, to do nothing is unthinkable."
She is just one of many celebrities who have forged long-lasting links with particular causes, putting her in a celebrity-charity category that audiences can accept, according to the PR agent Mark Borkowski.
There are three categories, he says: the Geldolfs or Bonos, who make a big noise about their charity work; those who give huge amounts of money without seeking publicity; and those such as Thompson and Elton John who pick a cause and use their profile to campaign for it over many years.
"There's always a delicate balance between the 'charidee' aspect that's often lampooned and the quiet donations," Mr Borkowski said. "The happy medium is a bit of both. Elton John has a hot-ticket charity that raises huge amounts of money as he tickles the ivories. Emma Thompson is using her celebrity without selling herself down the river, where the audience totally accepts the passion of the celebrity."
Not everyone is as enamoured with celebrity charity work. The TV pesenter Piers Morgan said: "I feel uncomfortable sometimes about the motives. I regard anything Madonna does with deep cynicism."
Emma Thompson and human rights
When not wearing bonnets in period dramas, Thompson spends much of her time in the murky real world of refugee rights. She is a patron of the Refugee Council and has unofficially adopted a Rwandan teenager.
Richard Gere and Tibet
The Buddhist founded the Gere Foundation in 1991, which has given millions of pounds to the Tibetan community in exile, the Dalai Lama and Aids research.
Oprah Winfrey and education
She has spent £30m of her fortune establishing the Oprah Winfrey Leadership Academy for Girls in South Africa.
Joanna Lumley and Gurkhas
Gurkhas think the actress is absolutely fabulous for helping them to win the right to settle in the UK last year.
Sir Paul McCartney and animal welfare
The former Beatle has a ticket to talk about anything he wants, and uses it to persuade people to eat less meat.
Jo Brand and mental health
The former psychiatric nurse is an advocate for mental health issues and won the Mental Health Trust Award in 2008.
Ruby Wax and mental health
Wax, who suffers from mental illness, has written books and made TV shows to address the stigma surrounding the issue.
Stephen Fry and bipolar disorder
Fry suffers from the condition and isn't afraid to talk about it. He was Mind's Champion of the Year in 2007.
Elton John and Aids
The singer may have more art than Sotheby's and enough flowers to fill Kew Gardens, but his Aids Foundation has raised £150m since 1993.
Emma Watson and Fair Trade
Hermione in the Harry Potter films may say she doesn't like the limelight, but that's not stopped her from using it to launch Fair Trade clothing for the ethical company People Tree.Reuse content