I like to find places close to the railway to watch or photograph trains - particularly prior to steam tours and such.
I always stay behind boundary fences and never go where I am not permitted to. I know the rules and I stick by them.
However, yesterday I encountered something rather puzzling. I was walking through a woodland that was easily assessable (no fences, signs etc), walked down a bit of a slope and looked for anywhere close tot he railway.
Walked for a while and then before I knew it, I was almost ON the railway

Naturally, I went back a bit from it encase of any passing trains. Don't want to panic any drivers and such even if I was a fair distance form the track. The only fence I saw was directly next to the track and I'm not certain whether this was a boundary fence or not because it was basically just stakes in the ground and wire between them.
I spend half an hour looking around for any more fences further back or signs - Found nothing! So as far as I can tell, I'm legally in that area and not trespassing but I've no idea how close I can legally get to the railway before it is considered trespassing.
I've attached some photos of the only fence I came across but if anyone have a bit more info on boundaries and how close people are allowed to get, I'd really appreciate it.