Game of Thrones has found its Mace Tyrell in Roger Ashton-Griffiths, while Joseph Gatt has been cast in a mysterious role.

We finally know who will be playing the key role of Mace Tyrell in Game of Thrones season 4, and it’s not Sherlock star Mark Gatiss after all: George R.R. Martin has revealed that British actor Roger Ashton-Griffiths has landed the role.

The seasoned actor is no stranger to historic roles, having appeared on such series as The Tudors, Henry VIII, Ivanhoe and many more.

Mace Tyrell is the son of Lady Olenna, and the father of Loras and Margaery. His role in Game of Thrones season 4 is likely to be a substantial one, considering events in the A Song of Ice and Fire saga.

Meanwhile, Game of Thrones has also cast Banshee actor Joseph Gatt, who most recently appeared in Star Trek Into Darkness.

Winter is Coming first reported this casting news, and has further discovered that Gatt has been filming on the Iceland set (where they primarily shoot the scenes beyond the Wall), and will appear in a total of four episodes.

Due to the location details, WiC speculates that the actor might play the wildling leader Styr. Do you agree?

We also recently reported that actress Indira Varma has been cast in the role of Ellaria Sand, the paramour of Oberyn Martell. Oberyn will be played by Pedro Pascal.

It’s great to see the new cast begin to come together!

Game of Thrones season 4 premieres spring 2014.