I do not accept your word "cannot" Strow. If a government thinks a move will make it popular, "cannot" would soon turn to "maybe". If subsequently a powerful lobby group proved to that government that there was a substantial majority in favour of such a move, "maybe" would very quickly turn to "will".
Who do you believe to be the stronger lobby group, NSBA or RSPB.
All the RSPB has to do is to prove to it's members that the only people who want the navigation to be protected are those people who are rich enough to own boats, and honest guv, it's "Bob's your uncle".
Yes my analogy was meant to be amusing, but, as I said some posts back, they only have to say "yes" once.
So!, If the government want's it and the BA want's it, then it's found that the general public wants it and the RSPB wants it, ... are you still saying it couldn't happen?