a couple of years back, in the course of one of my articles on Britain's looming energy crisis, I promised that the following week I would write about an astonishing revolution which could solve all of the UK's and the world's energy problems for centuries to come. I never followed this up, but what I was referring to was the incredible technical breakthroughs of recent years that allow almost unlimited amounts of cheap gas to be extracted from the world's vast reserves of shale, our commonest sedimentary rock.  It had long been assumed that nat