Ben wrote:

At least I now know which circuit is at fault.... all I have to do now
is determine what part of it! I assume I'm looking for a L-E (it didn't
trip when the circuit was switched off) and that the most likely

Alas not certain - a N-E fault could show up because the N may (quite
normally) rise a few volts when the circuit is loaded (depending on how
far you are along the circuit from the CU, and also on how "stiff" your
supply impedance is).

culprits are the garage circuitry or maybe the gas ignition. I think
the only appliance actually plugged in when it tripped tonight was the
hob extractor fan. Will do a quick check of that plug with the
multimeter, assuming that turns up a blank it'll have to be a call out
to a sparky.

Things with heating elements and things involving water in close
proximity to power are always likely contenders. Needless to say the
average kitchen is often full of things that match those descriptions.

You could always carry on playing the stepwise refinement game a little
more if required. You may find for example breaking the ring at a socket
half way round the circuit, disconnecting one end of the circuit at the
CU and running a temporary lash up cable from the CU to the break in the
circuit to make a new ring using the new cable plus half of the old
circuit.

Also if you can't find anything with a DMM, is there any chance you
could borrow a megger from someone?

--
Cheers,

John.

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