Captain America: The First Avenger director, Joe Johnston has previously stated that all six members of The Invaders would take part in the Word War II portion of the film. Now, actor JJ Feild (Centurion) is rumored to be playing the part of Montgomery Falsworth a.k.a. Union Jack.
The casting hasn’t been confirmed by the studio, and the only source currently suggesting Feild in this role is IMDB, and as such it should probably be considered rumor.