If you thought the main airborne threat in Game of Thrones came from Daenerys Targaryen’s troublesome dragons, think again.

Drones are the No. 1 aerial menace—on set, at least­. The production company behind the swashbuckling HBO fantasy epic has issued a strict ban on spy craft flying above the principal filming location in Northern Ireland.

Michael Macmillan, 58, the former Middle East bureau chief for the BBC who now runs a licensed drone-based aerial photography studio in Belfast, told The Daily Beast there was a proliferation of cheap drones equipped with Go-Pro cameras. He said freelance photographers might be trying to sneak plot-spoiling snaps.

“They are obviously not concerned about drones used by professional videographers like us, but unlicensed operators flying in lower-grade aircraft which can be used as a spycam,” Macmillan said. “They don’t want random shots being taken as the filming continues. There are also issues around invasion of privacy as far as the actors concerned.”

Macmillan said there were also risks of injury to cast and crew in the event of a crash on the set.

“In the wrong hands, a drone is an extremely dangerous object,” he said.

Signs erected by a security company on the fence of the filming studios in Titanic Quarter, East Belfast, specify that the area is a “no-fly zone” for the crafts and warn of prosecution for invading the airspace above the studios without permission from the Civil Aviation Authority.

A source told Belfast Live there were fears top-secret plot details could leak out if drones were able to hover above the site.

“I know there have been concerns about drones given the proximity to the airport,” they said. “There’s also a lot of concern around the risk of Game of Thrones and other shows being caught on the cameras of these things.

“This ensures everybody is safe and it retains the privacy of anybody filming here too.”

Macmillan said: “You are not breaking the law if you are not being paid to do a job, if you are just flying a drone for fun, but if your activities are presenting a danger you are likely to be infringing the law.”

However, as to what the producers can actually do about it if someone decides to flout their ban, the answer seems to be: not much.

Macmillan concluded: “If you were to take out a gun and shoot the drone out of the sky you could well be committing an offence yourself.”