Games of Thrones season 6: Castle Black set hit by rockslide during filming

'A piece of rock the size of a London townhouse just fell'

We all know Westeros is a place riddled with constant threat for its inhabitants, but who knew it spelled such dangers for those who make the television show as well?

While filming the upcoming season 6 of Game of Thrones, crew were faced with an unpleasant surprise when a sudden rockslide delayed filming at the show's Castle Black set. Located in Northern Ireland's Magheramorne Quarry, the castle's physical set lies next to a steep rockface; which in turn is dressed as ice and extended with CGI to look like The Wall.

Yet, Entertainment Weekly reports heavy rain beset the quarry during its winter filming schedule; which itself didn't interrupt filming as rain rarely shows up on camera, with the Battle of Castle Black shot during an intense downpour.

What it did, however, was disrupt the quarry's "seismic profile", leading to a dramatic rockslide in the area. As showrunner Dan Weiss explains, "Once people saw the small pebbles start to come down that turned into slightly larger pebbles, everybody made the group decision to immediately step away from the set."

"A piece of rock the size of a London townhouse just fell," vividly describes Owen Teale, who plays Ser Alliser Thorne on the show. Thankfully no one was hurt, but the rockslide caused major delays in what stands as a carefully orchestrated production, with scenes planned many months ahead.

"Bernie [Caufield] and Chris [Newman, producers] already have hardest scheduling job in the film and TV industry," Weiss continued. "And they had this thrown into the works too, which caused them to drastically reschedule the whole season on the fly."

"But they did it, and we got everything we needed in that quarry after it was seismically shored up and netted and proper protection measures were taken. It actually worked out for the best – some of the stuff we were shooting in that location benefited from the addition prep time the rockslide gave us."

In the US, season six will debut on HBO on the 24 April at 9pm. It will be simulcast in the UK on Sky Atlantic, at 2am on the 25 April. You can read about everything we know so far on the series here.