Knightley (Pirates of the Caribbean) and Dorman met on the set of Marie-Antoinette, and had been dating since August, 2003.
According to the Daily Mirror, "They both wanted it to work but in the end it was just untenable. They were having crisis talks on an almost daily basis so the decision was reached to finally call it a day."
Knightley is currently working on two films in the saga of Pirates of the Caribbean, in which she plays Elizabeth Swann.