English screen beauty Keira Knightley graced the red carpet for the world premiere of her latest costume drama, The Duchess, in which she plays a real-life ancestor of Diana, Princess of Wales.

Georgiana, the Duchess of Devonshire, was a celebrated beauty of her day, adored for her fine looks and fashionable clothes and her every move documented in the press but in private she was abused by her husband.

She was locked in a loveless marriage with the Duke of Devonshire, during which she was forced to bring up his illegitimate daughter and share her home with his mistress.

The trailers for the film draw explicit parallels between the two women.

One tagline is: “There were three people in her marriage” – a reference to the famous claim made by the princess in an interview with Martin Bashir.

The comparisons are inevitable – both were born Spencer and both ended up in unhappy marriages.

But Knightley played down the comparisons at last night’s showcase in London’s Leicester Square.

She said: “We certainly didn’t set out to make a film that was in some way about Diana.

“I think that Georgiana, Duchess of Devonshire, in herself was an interesting enough character to warrant a film entirely about her and not because there are any similarities with another person.”

She added: “She was an extraordinary person, a survivor. She goes through the most horrendous situations, yet somehow comes through them.”

The 23-year-old actress arrived an hour before the screening to sign autographs and chat to fans, looking radiant in a strapless, blue dress, chunky high-heels and Chanel jewellery.

Also at the event were co-stars Ralph Fiennes, who plays the Duke, and Dominic Cooper, who plays the future Prime Minister, Charles Grey, with whom Georgiana falls in love.

The film is based on the biography of Georgiana, written by Amanda Foreman, who was also at the showcase, joined by family and friends, including shadow chancellor George Osborne.

By Sunita Patel