Historically it's been the site we've used in the past, so if guessing for the purposes of planning an attack, wouldn't it make sense to use this as one possible point in that preparation? (plus possible other sites that may be likely)
Surely it's better to be safe than sorry?
If the person...
Member of the public is suspicious about the actions of a member of the public photographing a public building where a major gathering of football fans is about to happen (therefore reasonable suspicion? - as responding to a report from the public regarding his motives / behaviour)
Police...
He obviously wasn't known by those from the Police who questioned him or detained him, there are thousands of employees in the force in Sussex
Is the possibility of terrorism simply ruled out because of what, that terrorists simply could never get hold of such equipment for themselves? naive...
Or how about someone taking photos of a site that is about to have thousands of football fans descending upon it next weekend, does that not strike you as a possible risk location and worth investigating in order to try to keep those fans safe?
If they didn't and it turned out that the person...
So what else did he do to make the Copper come over to him to ask about it in the first place? If his just taking pictures doesn't seem enough for someone to ask him about it?
How does a terrorist take photos in a non suspicious way?, how does that vary from anyone else taking photos?
What do you think happens prior to a terrorist attack?
No planning, surveillance, etc? just turn up on the day and hope that you will be able to carry out your attack unhindered and as effectively as you wish?
Or do they spend time checking out their plan, taking photos of the place they wish...