And if a $US20,000 death is a little rich, there is a range of other prizes up for grabs. A mere $US4500 will get you a signed script of the first ever GoT episode; one of Martin’s trademark Greek sailor caps (pre-worn) will set you back $US7500; while $US15,000 buys breakfast with the master and the chance to quiz him about GoT minutiae.

In addition, everyone who forks out for the campaign will go into a draw for a day out with Martin.

"You and a friend will be flown out (from wherever you are in the world) to meet me in Santa Fé, where we'll share a helicopter ride to the Wild Spirit Wolf Sanctuary," writes Martin. "If there's anything you have ever wanted to ask me, here's your chance!"

Meanwhile, US cable network HBO has announced that GoT has surpassed The Sopranos as its most popular series ever.

Episodes in the fourth season of the show have an average gross audience of 18.4 million, including repeat showings, video on-demand and mobile streaming, which broke the record of 18.2 million set by the 2002 season of the mobster drama, The Sopranos.