Former THE O.C. star Mischa Barton is reportedly romancing Keira Knightley's ex Jamie Dornan, after the pair were spotted together in London earlier this week (14MAR07). The actress was seen leaving an Arcade Fire gig in Brixton on Wednesday night (14MAR07) with model Dornan by her side. Barton, 21, split from her boyfriend of 18 months, rocker CISCO ADLER in February (07), while Dornan ended his two-year romance with Knightley in late 2005.