Unfortunately the "national trust" in the UK have acquired vast tracts of land in the UK including thousands of miles of coastline. Ostensibly to preserve it but in reality most of the land isn't touched.
They have banned drones over *ALL* of their land and properties making huge chunks of the UK theoretical no-go zones. They also make large amounts of money selling people pictures taken with their own drones.
They've done a similar thing banning all commercial photography on those lands so taking a photo of a 2 million year old, untouched rock and selling it is now illegal. They went after several stock sites demanding tens of thousands of images were removed a few years back.
NT also have a habit of buying up public land and charging for previously free car parks whilst restricting public access to that same land. The organisation as a whole has a reputation for bullying.
There is some debate about whether the ban on *overflight* is illegal or not. There MAY be a legal decree meaning they have the right to do this but to date they've never provided it when asked. Launch and landing on the land is banned though.
They claim its for "safety" but in reality the risk of someone flying a drone over a massive wilderness, lacking in any people are nil.
FWIW pretty much all castles in the UK have the same ban along with other historic buildings and landmarks.
You MAY be inside the CAA mandated 50m from property on the video but its hard to tell and if so, not by much.
So the guy is potentially right (albeit an arsehole). If you launched from or flew over national trust land you could well be operating illegally. The fact the NT is a fairly odious body unfortunately has nothing to do with the legality.
Looking on (
Follow the history of our places with Land Map ) they do seem to own the beach, cliffs and inland for many miles around that area.
