– “so why do you think different governments have not been in favour of a Severn Barrage?”
Michael, I do not know. Possibly governments have dismissed it on grounds of cost and its novelty, possibly due to lobbying by the nuclear industry which is very powerful due to its connection with weapons and the military, possibly due to pressure by environmentalists; a barrage would surely have extensive effects upon ecosystems in the estuary, the nearby coast and upstream, though I expect all could be addressed in its design. Probably a bit of all three. It is something I have not investigated, neither politically nor environmentally.