Came in too late with this job, the cable had already been laid(not sure how deep!),
Meggered it and got 150Megohms between the NS
and all phases.(@1000V)
Will drive a stake.
Ever bent a stake in stony soil?, done it for the first time, last week, out at the local abbattiors, installing a 600A sub-main, the stake started to come up through the ground about 3 foot away from where I was driving it.