I'm on Green Lane as well - AND I have just put 2 new 'cube' planters outside the front door!!!! Yep, they are heavy and they will be even heavier soon when they are planted out with the Box trees. Still, I do not want them to be nicked. We do have cctv
but all that does is prove they have been nicked! Does not tell you who did it.
I think the best plan is a Rawlbolt into the concrete path through a hole in the bottom of the planter and a very large head washer under the bolt head. That will stop anyone moving them.