Clark, so why do you think different governments have not been in favour of a Severn Barrage?
It would, for three hundred years, produce renewable electricity of 1/20th of the entire needs of the U.K.
It would help prevent up-river flooding, at times something that can be devastating.
Most of the turbines would turn most of the time, this could be envisioned as base load. There could be road and rail links along the top between Somerset and South Wales. It could be associated with wind turbines for extra pumped storage.
Yes, it would use an awful lot of Limestone, a downside and it might take fifteen years to complete.
It would provide a model that could be used in other parts of the World.