Hafþór Júlíus Björnsson is a professional weightlifter and former silver medalist in the World’s Strongest Man competition. He also plays Gregor Clegane, aka The Mountain, possibly aka Ser Robert Strong (minor spoilerage, but not really) on HBO’s Game Of Thrones. He once declared himself the “future of strength.” I’m inclined to let him have that one.
Cersei never saw where Qyburn came from, but suddenly he was there beside them, scrambling to keep up with her champion’s long strides. “Your Grace,” he said, “it is so good to have you back. May I have the honor of presenting our newest member of the Kingsguard? This is Ser Robert Strong.”
Ser Robert Strong is a knight acquainted to Qyburn who is a giant of a man, eight feet tall. He is to fight for Cersei in her trial-by-combat. King Tommen names him the newest member of the Kingsguard.