<em>Game Of Thrones</em> stars look smouldering as they attend the season 5 premiere at the Tower of London

London - The fifth season of Game of Thrones had its premiere on Wednesday at the Tower of London, an atmospheric landmark whose history is like the show: tangled, royal and bloody.

The series' stars walked a red carpet at the 1 000-year-old fortress, a former palace and prison where traitors were once tortured and executed.

"Just think that 200 years ago we'd be coming here to get our heads chopped off ... (not) watch the telly," said Liam Cunningham, who plays the knight Davos Seaworth.

The cast were sworn to secrecy about plot twists in the series, a phenomenon that has injected sex, blood and plots of Shakespearean complexity into fantasy television.

But Michael McElhatton, who plays Roose Bolton, promised "shocks" for fans of George RR Martin's books, on which the series is based.

Nikolaj Coster-Waldau, who plays Jaime Lannister, added that "there will be major surprises. We enter the endgame now."