Do You Have Permission

I went down to the waterfront tonight only to bump into the overzealous security guard. This is how the conversation went,
Him; what are you doing?
me; taking a few photographs of the frozen canal basin
him; do you have permission
me; no, I didn't realise that I needed permission
him; you have to get permission from the site owners
me; ok no problem, do you have a phone number and I will call them now
him; there is nobody in the office now
me; ok, I'll bear it in mind next time I come here
him; you can't take pictures here, it is private property
me; sorry I'm going now
him; it would be the same as me coming into your back garden without permission and taking photos.
me; not really because my back garden IS a private place whereas this canal basin is a public place and is not fenced off or locked up
him; it is private and you can't take pictures
me; ok mate I get it , now fu****f and I'll be on my way
him; but it is private.
At this point I was going to throw the twat in the water if he didn't just shut the f**k up and leave me be..
The problem I have now is that I will see it as my moral duty to wind this idiot up at every oppurtunity so expect more from the waterfront soon.