This is Sam Hoare. He's been in things like Captain America: The First Avenger, Legend, and The Golden Compass. And there is a possibility he's going to be playing Harold Grey who is Lord John Grey's older brother.
Harold Grey is Duke of Pardloe, Earl of Melton and Colonel of the 46th Regiment of Foot. He is also the older brother of Lord John Grey.
Starz hasn't confirmed this speculation but this cryptic tweet from Hoare got him a lot of Outlander fan followers...
Could HA and GR mean Hal Grey?
Click Follow above to follow this Sam and you can check out his credentials on IMDB.