There is zero chance this was a mistake, it’s the only tree in the area and to say it’s iconic in the North East is an understatement - this was a deliberate act, the only thing in doubt is their state of mind.
From a legal perspective, this isn’t an issue. It’ll be a brave barrister that tries to argue a lack of intent when someone travels to the arse end of nowhere with a chainsaw and cuts a well-known tree down. I’d honestly expect the judge to throw the hammer at anyone who even tried.