Stars of the blood-soaked fantasy such as Kit Harington (Jon Snow) and Sophie Turner (Sansa Stark) attended the launch at the Tower of London, the scene of a host of past power struggles, torture and executions.
To mark the event fires were lit around the turreted castle, which like many of the strongholds in the universe invented by author George R. R. Martin is home to a colony of captive ravens.
Michael McElhatton, who plays the grim Lord of the Dreadfort Roose Bolton in the series, said the story travels southwards to the kingdom of Dorne in the fifth season.
“The world has just got bigger and bigger and we are going to move into the world towards Dorne a lot more and introduce a lot of new characters there,” said McElhatton said.
“There’s a lot of shocks particularly for the book readers. There are things that happen now that aren’t in the books.”
The most-watched show ever by US television network HBO, Game of Thrones tracks the violent and often nudity-filled struggle of rival families to rule from the Iron Throne.
Asked why it was so popular, Harington (Jon Snow) said the show was not deliberately provocative.
“I think it’s what makes our show our show and I don’t think it’s controversial for the sake of it,” the 28-year-old British actor said. “It’s complex and it doesn’t treat audiences like idiots.”
Hundreds of fans gathered at the castle beside London’s river Thames to catch a glimpse of the cast at the premiere, the first to be held in Europe.
Alfie Allen, who plays Iron Islands heir Theon Greyjoy, said the new season would bring “shocking scenes without a doubt”.
“I’d like to see how much farther they can push the sort of dark side of it as a show as a whole,” Allen said, adding that there is “maybe a little bit of light at the end of the tunnel” for his character.
“It’s done in a very clever way,” Allen said.
The series is due to be released from April 12.