TSRGD is the Traffic Signs Rules and General Directives - basically the specification for how signs and markings should be used, and what regulations they apply to. I became familiar with it after looking up a few things. Only really useful to people who don’t work in related industries as a way of getting out of tickets or fines or whatever when the sign/marking/etc was non-standard. Sites like Pepipoo rely on it.
But yeh, I can understand the motivations for stopping there. I would rather have infringed a few minutes to find somewhere that wasn’t on the brow of a hill, on a bend infront of a side road, though. Attitude didn’t help tbh.