The 27-year-old actor will team up with Vikander in a new big screen adaptation of Vera Brittain's World War I memoir, 'Testament of Youth', said The Hollywood Reporter.
Vikander, who replaced Saoirse Ronan in the 'Game of Thrones' last year, will play the famous writer Brittain with Harington starring as her fiance.
The project is being directed by James Kent of 'The White Queen' fame. It would be produced by BBC Films and David Heyman, who produced the successful 'Harry Potter' series and the 2013 film 'Gravity'.