"Andrew Dunbar was an actor who was also a stand in as Theon on GoT," wrote Allen on his Instagram stories. "Extremely shocked and saddened to hear of his passing. To lose a love one so young, I can only imagine what his family are going through. RIP Andrew xxx."
Dunbar had also appeared in the shows Dery Girls and Line of Duty, among others. He reportedly died on Christmas Eve at his home in Belfast, Northern Ireland. His death is not being treated as suspicious, although a cause hasn't been revealed.
The Extras Dept. agency released a statement on Dunbar, who was reportedly in his 30s. "To say we are shocked and saddened at the passing of Andrew Dunbar is an understatement," said a spokesperson for the Northern Ireland extras agency. "We have so many fond memories of the years Andrew worked with us. He was so versatile we could cast him in anything, he was such a talented performer he would always end up being featured, and he was so adored that he was always requested by productions again and again. [...] Thank you for all you did for us Andrew. We will miss you dearly."
As well as standing in for Allen, Dunbar fought alongside Kit Harington's Jon Snow in the "Battle of the Bastards" episode.