Hmm, Greebo and I watched it being built/thrown up, and the fences (i.e. the "feature" wrought iron fencing, not builder's mesh and fence rods) were up before the place was finished, especially at the back, and it's certainly the case that they stuck in the street-access and park access gates pretty late in the day - in the case of the parkside gate they had to pretty much chop out a lump of their fence and then "sculpt" the slip into the park - and I think the Friends of Brockwell Park newsletter had something about a felling licence having to be granted to remove a tree that was in the way.