Hummm interesting when someone can have some clues regarding the types of screw used....
But I warn you Airframes, this one is a tricky one because of the point of view.
Okay now I shut my mouth ! too much informations, I am afraid to offer an easy Beer
Not saying the photo is inverted, just trying to figure out, for myself, what angle I'm looking at. Afraid I don't understand the clue though, but no problem, I'll keep thinking!
Now you are saying that, I am not exactly sure this is a "law" but this is a decision from UK governement about this aircraft as far as I remember...
I think you guess what I am talking about ? ...okay last clue from the last clue : Margaret Thatcher
The 'bolt', or turn button, looks like a typical WW2 era cowling fastener, as seen on Spits and Hurricanes, but I can't see a Margaret Thatcher, or a 'law' connection - puzzled!