The head end is fed directly from the meter into a small consumer unit cont aining a main switch and a 20A type B MCB. This is the one that trips. This connects to around 100m of 6mm SWA, partially buried, partially running ab ove ground through some brambles (will get around to burying that one day!) . I have completely disconnected the SWA in the garage.
There was a resin-filled join in the SWA around a third of the way, so I cu t that out as that was what I suspected of being the problem. If I connect just the first third of the SWA to the head end it doesn't trip. If I conne ct the rest it does trip, so the problem obviously exists in the final two thirds of the cable.
I've used a standard multimeter to test the resistance between L&N, L&E and N&E but all read open circuit (the meter shows a reading for an instant, t hen reads open circuit again). I don't have access to a Megger unfortunatel y.
I've visually inspected the parts of the cable I can get to, so now I'm stu ck for ideas.
Any suggestions for how to proceed would be gratefully received!