However before doing so, the concept of “security of energy supply” must be defined and understood as it applies to the formulation of government policy. Energy supply security is a many-splendored notion that can mean very different things to different people. A foreign policy expert will look at the issue differently than a network engineer or an economist. Definitions of what is security of energy supply by different experts abound but they are often too abstract to come to grasps with the concrete issues intrinsically linked to geopolitical preferences, strategic technology choices and fundamental orientations of social policy.