No fly zone around Windsor Castle, London
But it may give some backside covering value in the event of an incident that might expose people to the question of "why was there not a no-fly zone?"
About 15 years ago, a friend took me and SWMBO on a very posh helicopter from Denham to Farnboro and back. With some er, interesting "pretend" landings at Farnboro. His clearance to fly thru the notional no-go area around LHR flightpaths was granted in about 5 seconds by the ATCO. I guess they are used to the Royalty flying in to and around Windsor.
This whole thing could not be more of a "non-story". It will change nothing at all.