The company that brought Game of Thrones to a global TV audience has formally ended its tenancy of more than 10 years at Titanic Studios, the Belfast Telegraph has learned.
HBO filmed multiple seasons of the hugely successful fantasy drama at the Belfast landmark.
The US cable and production giant has now issued a 'letter of notification' to Titanic Quarter, Northern Ireland Screen and others connected to the studios, stating that it no longer needs the facilities.
After Game of Thrones ended last year, and the shooting of a pilot for a now-scrapped prequel stopped, there remained an effective agreement that the studios would stay vacant, and not be marketed for use by others, until the notification was issued, according to NI Screen.
A separate 10-episode Game of Thrones prequel - to air on HBO's new streaming service - is currently in pre-production but will not be filmed in Belfast, NI Screen chief executive Richard Williams confirmed.
It was known from a relatively early stage that Northern Ireland was not in a position to deliver, in location and other ways, on what was required for the prequel series, provisionally titled House of the Dragon, Mr Williams said.
"All that is happening... is that they have served notice to Titanic Quarter that they would not be holding the studios," the chief executive said, adding that NI Screen had encouraged HBO to do so as the space could not be sold to others until this happened.
He added: "There is no surprise here, no panic."
Filming of the pilot for the other, abandoned prequel starring Naomi Watts and Miranda Richardson took place earlier last year, but HBO said it would not be moving forward with a full series in early November.
Trade publication Deadline reported that it was scrapped following a long post-production process, including re-editing. Other outlets reported budget overruns and creative differences.
Mr Williams said his organisation and others in Northern Ireland maintain an "extremely close" relationship with HBO, which he described as "our best friends in Hollywood and I do not think that is ever going to change".
Over the years, NI Screen supported the series with £15.94m in funding, but the production is estimated to have added approximately £250m to Northern Ireland's economy.
Tim McKane, a communications specialist and former board member of NI Screen, said any criticism of the organisation over Game of Thrones is a "lot of nonsense".
Mr McKane described the partnership as a "phenomenal" success.
With Netflix, Amazon Prime, Disney and Apple set to spend billions over the coming years, there "has never been a better time because of the demand for content, and they have to make it somewhere", Mr McKane added.