Recent 44++ Lily James Mamma Mia 2 Cast. She's best known for playing lady rose in downton abbey and lily is now starring in the darkest hourcredit: With the film's original cast returning and new additions including lily james. Lily chloe ninette james (née thomson ; Born 5 april 1989) is an english actress. Lily James Mamma Mia 2 Cast - Mamma Mia 3 Everything We Know So Far Has officially wrapped filming was shared by downton abbey star turned hollywood actress lily james on instagram.