Stephen Dillane, who starred as Stannis Baratheon for four seasons, confessed that he had to rely on their co-stars to help them understand the plot.
“I’ve flicked Game of Thrones on since leaving to see if I could figure out what was going on, but I couldn’t,” the actor noted.
“Liam Cunningham is so passionate about the show. He invests in it in a way that is quite moving, but it wasn’t my experience.
“I was entirely dependent on Liam to tell me what the scenes were about – I didn’t know what I was doing until we’d finished filming and it was too late.”
He went on to tell The Times: “The damage had been done. I thought no one would believe in me and I was rather disheartened by the end.
“I felt I’d built the castle on non-existent foundations,” he continued.
It comes after Liam, who stars as Ser Davos Seaworth, teased “huge surprises” in season eight with a “bittersweet” final.
Following the first read through of the scripts, the actor explained: “It was all new to us, and it is just, ‘Oohs,’ and, ‘Aahs’.
“It is as it was in the past, it is just beautiful storytelling. Huge surprises. Wonderful stuff. I can safely say it will be a fantastic, fantastic finish to this incredible story.”
Game of Thrones is expected to return to Sky Atlantic in 2019.