Everyone now recognises that fuels and the energy they contain are amongst the most important factors in the economy and it is accepted that it is only sensible to YIe them in sound and efficient ways. Since the Second World War there has been a number of fuel 'crises'; a build-up of supplies just after this War, then the return of fuel oils to the market, followed in the 1958:62 period by a steady fall in the delivered prices of fuel oils. In turn this caused the contraction of the coal industry, closing of many pits then considered to be uneconomic and ever-increasing imports of crude oil for processing in refineries. The ever-increasing demand for energy all over the world has continued without interruption for nearly thirty years since 1945, with periodic warnings from conservationists that an energy 'gap' would hit the world at some indefinite period towards the 1980-90 period. However, such vague warnings carried little weight with the majority of users when abundant supplies of cheap fuel oils continued to be available.