Socket with earth fault

[John Rumm]

A damaged or crushed cable seems most likely then...

Short of exotic test equipment like a TDR setup you may be stuck. Any place you could route an alternative?

[<me9]

My upstairs lighting cable was discovered to have a broken earth. This was due to the original builders crushing the cable between a floorboard and the breeze block wall. One of the other conductors was also damaged, and came apart with little provocation.

If it is a broken earth conductor it needs to be found and repaired, or the complete cable run replaced. Do not use a cable with one suspect core, there will almost certainly be more damage..

[John Rumm]

There is no reason your replacement cable has to run the same route though - it could be surface wired behind the cupboards for example to make life easier.

[John Rumm]

When I rewired my former neighbours house a few years back, I found a standard 5A junction box joining three flexes, just buried in the plaster plaster about a foot above the kitchen sink! (not sure if he owned up to that one or not ;-)