Hi Raymond,
Welcome to the forum.
The general recommendation is to exercise common sense spotting and photography, which would involve taking said required photo then retreating 3 metres from the security fence so as not cause angst or alarm to security.
Probably not a good idea to touch/lean against any security fence with your person or ladder..... and don't forget to remove any ladders or tripods you may take along with you.
Of course, if you loiter you may attract unwanted attention, so be sure to always carry suitable ID.
Good luck with the photo
