It has an RCCB (Residual Current Circuit Breaker), the main switch that the shore power live and neutral is wired into. A standard Residual Current Circuit Breaker (RCCB) does not trip solely because a wire is overheating due to an overload or poor connection, because it lacks integrated overcurrent protection. It will only trip if the overheating leads to an earth leakage fault. Hence in my case, this did not happen.
The live had probably been work hardened over the years and stands started snapping at the RCCB causing an overheat, at least that was my initial thought. It looks like it was the neutral that gave up the ghost by overheating, melted and scorched the live causing that to overheat, probably a combination of both.
However the main point is that an RCCB will not trip when only overheating happens. An RCBO (Residual Current Breaker with Overcurrent protection) can and should trip if a cable overheats. I bought a new consumer unit, with a main power switch RCBO and the various circuit breakers, also RCBOs.
If you have an old consumer unit, it would be worth changing to the new style with an RCBO. The whole box will have to be changed, especially if like mine, it was not a DIN rail type (common mounting system). In addition RCBOs have an extra neutral wire (flying lead built in by the manufacturer) that connects to the incoming neutral, unlike the old RCCB style, which don't have the flying lead. Total cost from Screw Fix in Oban was a tad over £50 for the consumer unit which only comes with the main switch RCBO, in addition I purchased 3 x circuit RCBOs separately rated for the circuit wires (ring main, water heater and spur in my case). A good cost for modern electrical safety.
Please note that I am an amateur and this information is based on my research, do your own checks and consult an electrician. Apart from the extra neutral wire (flying lead) on the RCBO, everything else was the same for wiring up, so a near like for like change out. The new consumer unit has a bus bar for the flying neutral leads, which older consumer units will not have.
