Quick answer
In a concentric service cable the phase conductor runs down the centre and the neutral is laid as a complete layer of wires around it. Tapping the phase means first cutting through the energised neutral layer — difficult to do, and easy for the utility to detect. It is the standard construction for house-service connections where pilferage is a problem. Two arrangements exist: CNE, where the concentric layer is combined neutral and earth, and SNE, where neutral and earth are separate wire sets in the same layer. See concentric anti-theft cables.