I accept this, but I am a commuter that has taken pictures of things (like the work being done at Finsbury Park, which is ongoing) and been told I need to sign in and get permission to take photos.
Now, I do agree that if I was to go there simply to take photos and not while waiting for my train, I'd sign in. If I was taking commercial photos I'd seek permission in advance of going there. However, the guidelines only state you need to inform someone - not request permission. Why should a station manager get to decide by what you look like, or what mood he or she is in? That's surely why there are guidelines?
Now, asking someone to keep away from a certain area or being strict with anyone that doesn't keep the guidelines (camera flash, tripod causing obstruction, abusing staff/public) is fine - but it seems that some staff simply hate enthusiasts and therefore get off on 'playing' with them.
Cameraphones now mean anyone can take photos. Tourists aren't stopped. If, as I travel on my train right now, decide to take a photo out of the window - should I have got permission? What if I take a photo of the seats in front of me?
Someone Tweeted to FCC only this morning about the state of the interior of a train. Should they be told off for taking a photo without seeking permission?
Or is it what you're taking a photo of? I take the camera out and take a picture of my wife next to a gateline, that's fine. I take a photo of the new gateline without my wife in the picture and I need permission due to the 'heightened security risk'. (Tip; terrorists, travel in a group and pretend to be confused tourists).
It isn't very well thought out is it?