Britain could produce about a dozen nuclear powerstationsworths of electricity by building the Severn barrage, and more still with tidal barrages across other estuaries. However, that would wipe out a vast area of intertidal zone that is the habitat of many of Europe's wading birds.

I suppose a 30km Straits of Dover barrage would produce still more, but annoy all northern Europe's shipping. But a Mull of Kintyre barrage, now there's a thought- a 20km road/ rail bridge to Ireland included. Or even a dual Kintyre/ Galloway barrage. However, Scotland having provided all the oil for the 80s and 90s, they might baulk at providing England with power for all time, and there might be a secession creating a Scotland/ Northern Irish/ Republic state, energy rich but leaving England in the lurch.