George R.R. Martin aiming to release 'Game of Thrones' book 'Winds of Winter' in 2021

Game of Thrones writer George R.R. Martin is aiming to release the latest book in his A Song of Ice and Fire series next year.

The writer has said that the coronavirus lockdown has allowed him to spend 'long hours' working on the long-awaited tome, called The Winds of Winter, though he is running into issues with 'cabin fever'.

In a blog post published yesterday, Martin wrote: “If nothing else, the enforced isolation has helped me write. I am spending long hours every day on The Winds of Winter, and making steady progress.

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“I finished a new chapter yesterday, another one three days ago, another one the previous week. But no, this does not mean that the book will be finished tomorrow or published next week. It’s going to be a huge book, and I still have a long way to go.

“I have bad days, which get me down, and good days, which lift me up, but all in all I am pleased with the way things are going.”

Martin began working on the novel, the sixth in his epic fantasy sage, in 2010, a year prior to the series being made into the hit TV show.

The first three books, A Game of Thrones, A Clash of Kings and A Storm of Swords, were all published in short order, between 1996 and 2000.

However, the 71-year-old writer's pace has since slowed, with A Feast for Crows arriving in 2005 and then A Dance with Dragons in 2011.

As the production of the HBO adaptation of the books ploughed on, Martin briefed showrunners D.B. Weiss and David Benioff with a roadmap of how the books would end.

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However, as the series overtook the books, fans and critics began to increasingly criticise the show, notably the final series, which was slammed for its quickened pace and focus on action set-pieces over the previously nuanced drama.

The Winds of Winter and A Dream of Spring will be his final two books in the series.

Martin also briefly mentioned the development of the prequel series The House of the Dragon in his blog post, adding that it is 'flying along wonderfully'.

The show will delve into the history of the Targaryan family.