"Bicycles will be removed" - legal?

even better would be a sign attatched to the bike, saying 'this bike is being left here as a experiment into the legality of removing property which does not belong to the remover, feel free to take part, we are watching you!' and see if anyone wants to go ahead. I think they might not bother..

When I was working as a courier I had, for a short time, a double-sided laminated sign zip-tied to my top tube that read something like:

"Anyone attempting to remove this bicyle will be prosecuted for theft and / or criminal damage, without exception"

It didn't last long as the rain got to it and was also unnecessary as I ignored all those signs and never had any trouble (except once)...but then a courier generally only stops for a few minutes.