When we started rebuilding ours, one of the first things I found was rubber covered meter tails running through the house to the consumer unit…. Cant remember what it was called…. But anyway, the rubber had hardened and perished in many places… bare incoming, just behind the coving!!! To avoid issues, I Replaced them before calling in the electric suppliers to move the meters.
VIR - Vulcanised Indian Rubber, phased out in the 50's