In August, Broadbent — who played Potions Master and former Head of Slytherin Horace Slughorn in Harry Potter franchise — was announced as the first official cast addition for the upcoming season. Entertainment Weekly revealed that the Oscar-winner (for his supporting role in 2001's Iris) would be playing a "significant" role, but that's about all anybody knew until now. During an interview for his new drama The Sense of an Ending, Screen Crush offhandedly asked Broadbent about his part on Thrones. He joked that he couldn't say anything — before saying, well, quite a lot.