"They're absolutely paranoid now about anyone finding out anything about the series and spoiling it," he said.

"We weren't allowed a written word on a page."

The final season of Game of Thrones will be shown on Sky Atlantic in April 2019.

Glen said: "Everything was accessed through iPads with different security you had to get through to access it. Which caused a problem for the actors, I have to say."

Iain Glen as Ser Jorah Mormont with Emelia Clarke as Daenerys Targaryen

The Scottish actor, who has played Ser Jorah Mormont in HBO's global phenomenon since it began in 2011, also said that the show's final season is "absolutely phenomenal".

Speaking to BBC Radio 5 Live's Nihal Arthanayake, Glen described the table read for Game of Thrones' final season, which saw more than 100 cast and crew gather together to read through the scripts for all six episodes.

"This season was the first ever that we sat and read the entire arc of the story from beginning to end right through over the course of a day," he said.

"Kit [Harington - who plays Jon Snow], if he wasn't lying, had not read it, so he was reading it on that day for the first time."

Iain Glen says the cast are really pleased with the writing for the final season

Glen said there were moments of shock from the actors, as they realised how the show's intricate plot was set to be resolved, but that the consensus was that the actors were thrilled by what had been written.

"Honestly, these six episodes are absolutely phenomenal. The writers really, really came up trumps. The way they pulled it all together was a real writing task.

"There were a lot of tears that day... and it's been a season of that because it's been a season of farewells and finishes."