I have only had trouble with with the goons outside London Aquarium. The river bank walkway there is owned by the company, it is only a public right of way with their permission which can be withdrawn at any time. I was sitting eating a sandwich, my camera was on a tripod next to me, it was switched off.
"No pictures" said the goon...."No pictures"
"I am eating....I am not taking pictures, the camera is off"
"Take it off the tripod, tripod not allowed to take pictures"
"You got it wrong mate, the camera takes pictures, the tripod holds the camera"
"Take it off the tripod"
"I am eating my sandwich, when I have finished I'll be gone anyway"
"You must take it off now.....take pictures only with no tripod"
"I cannot take pictures unless my camera is on a tripod, I have Parkinson's disease. If everyone else can take pictures except me....you are discriminating against me"
long silence, furrowed brow "I will speak to my supervisor"
He marched off.....I finished my sarnie and left after whacking out another couple of shots with my camera on the tripod before he came back.