Speaking with James Andrew Miller in his book Tinderbox: HBO's Ruthless Pursuit of New Frontiers, former WarnerMedia chairman Bob Greenblatt outlined exactly what went on.
Greenblatt said: "They had spent over $30 million on a Game of Thrones prequel pilot that was in production when I got there.
"And when I saw a cut of it in a few months after I arrived, I said to Casey [Bloys, HBO’s chief content officer], 'This just doesn't work, and I don't think it delivers on the promise of the original series.' And he didn't disagree, which actually was a relief.
"We unfortunately decided to pull the plug on it. There was enormous pressure to get it right and I don't think that would have worked."
The canned prequel series, which would have starred Naomi Watts, was said to be set 'thousands of years before the events of Game of Thrones'.
A synopsis read: "The series chronicles the world's descent from the Golden Age of Heroes into its darkest hour.
"And only one thing is for sure: from the horrifying secrets of Westeros' history and the true origin of the White Walkers, to the mysteries of the East and the Starks of legend... it's not the story we think we know."
Despite this series being scrapped, another prequel House of the Dragon followed hot on its heels - and is due to be released next year.
Greenblatt said of House of the Dragon: "I'm the one who encouraged Casey to greenlight it to series.
"I said, 'Let's not risk $30 million on a pilot.' You can't spend $30 million on a pilot and then not pick it up.
"So I said, 'Let's not make a pilot. Let's get a great series that we feel good about, and just make it. Or not.'"
Greenblatt went on to explain how HBO was 'minting so much money' that it had 'lost a lot of discipline'.
At the time HBO announced the first prequel was being shelved, the company didn't provide much of an explanation.
In a statement given to Insider, it said: "After careful consideration, we have decided not to move forward to series with the Untitled Game of Thrones prequel.
"We thank Jane Goldman, S.J. Clarkson, and the talented cast and crew for all of their hard work and dedication."
House of Dragon is set to premiere in 2022 and will tell the tale of House Targaryen and the Targaryen civil war that became known as the 'Dance of the Dragons.'
Featured Image Credit: HBO
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