The pair fell for each other on the set of the ABBA-inspired musical last year (08), with Brit Cooper allegedly starting an affair with Seyfried while he was on a temporary split from his girlfriend of 12 years, Joanna Carolan.
Earlier this week (begs17Aug09) speculation mounted that Cooper was romancing a new co-star - Irish actress Ruth Neega, who appears with him in the Greek tragedy at London's National Theatre.
But it seems Cooper and Seyfried's relationship had already fizzled out - the blonde beauty spoke of her love life in an interview with this month's (Aug09) edition of British magazine Allure.
She told the publication, "Things end. Things end. And we're in a weird business. We're surrounded by just strange people, strange influences.".