Starting with evidence that United Kingdom Continental Shelf oil and gas companies have benefitted very disproportionately from the recent period of very high oil prices, this research traces the history of this weakness in the UK's petroleum fiscal regime. Evidence is provided that the progressive relaxations in the UK's petroleum fiscal regime in 1983, 1987-88 and 1993 were: largely unnecessary to stimulate the development of new, smaller, 'marginal' fields; misguided in their assumption that such fields were more costly to develop than earlier counterparts or larger contemporary fields; and impotent compared with the effects of oil price movements. The paper concludes with a conceptualisation which illuminates why these failures of policy were not just random: they emerged from the UK's 'non-proprietorial' stance with respect to the country's oil and gas resources, a stance which assumes responsibility for oil company profitability and vainly tries to counter market forces at the expense of government revenues.