To understand ring main visualise a circular loop of wire (three core, two for the mains and one for ground) connected at one point to the mains input and to a number of take off points elsewhere in the ring. The idea is that power can reach each outlet by travelling clockwise and anti clockwise. Apparently this means that lighter wires can be used for a total amperage load or perhaps there is an economy on not having separate wires running out like spokes to each outlet. I always thought that this was a uniquely British practice and I would be very surprised if France /Amel used the same system.
