Sienna Miller has joined her partner Tom Sturridge at the premiere of his new film.

The pair joined his co-star Dakota Fanning at the London launch of Effie Gray - the true story of a scandalous Victorian love triangle.

The US actress plays the title role in the film which was written by double Oscar winner Emma Thompson.

Gray was shunned by polite society after her marriage to art critic John Ruskin was annulled and she went on to marry the painter John Everett Millais, played in the film by Tom.

The pair are said to have fallen in love when Millais painted her husband's portrait and the story has already inspired a handful of plays, novels and films.

Tom said he researched the part by studying the painter's work hanging in the Tate Gallery. He said: "The first thing you do when you're reading about artists is you go and see their work and I think what attracted me initially was just looking at Millais' paintings, the eye he very clearly had which I think was reflected in the story by which I mean this is a story about someone who listens to somebody more than somebody else and the way a painter sees things that other people don't see."

He was full of praise for the "amazing" Dakota who is going out with one of his best friends Jamie Strachan, but denied having anything to do with getting the couple together.

He said: "I'm the worst at connecting people."

At least two members of the cast - Dakota and veteran Italian actress Claudia Cardinale - admitted the film's period setting and its costumes were a big part of its appeal.

Dakota said: "I've always wanted to do a period film so it was very exciting to get to fulfil that dream and wear those costumes."

The cast of the film, which has its world premiere at the Curzon cinema in London's Mayfair, also includes Julie Walters and David Suchet.