Thanks Group9. I now see where the laws differ.
In our instance (mooring fields) it would take a pretty good lawyer to argue that navigation is impeded as in the example of the OS/BLX bridge. That is to say, in a historic anchorage whereat navigation was really already impeded, yes? And of course Trinity could afford good lawyers. I've not yet seen anything come out of the Trinity yard which challenges anything near that bridge height
only a couple of gin palaces, ha ha
It appears, ltgoshen, that Group9 has offered your answer. Got lawyer?