…and TSRGD, by default, would have a 560 as flat, not curved as it would be if fitted to something like an Admiral. So I think you’d have to argue, as Simon says, that the reflector attached to the bollard isn’t a sign due to the curvature.

This is why things like the Ensign and Mini-Ensign bollard, although the bulk of the product is circular, have flat areas for fitting signs onto.

Quite where “flat” would put something such as a Flexmaster legally, is another – but closely related – matter.