Victoria Clare wrote:
It's rock, but it's not what I'd call solid. It's nasty shaly flaky stuff
that cracks easily and I would have thought sideways leverage would
probably crack it in an annoying manner.

Sorry, I forgot where you are, now I know what your soil's like
- your best bet is a steel pole, 1" or so in diameter, sharpened
at one end, which you thump up and down in the hole. Remove bits
and pieces of rock as needed.

If you're putting a gate in a hedge, then if you connect the
top of the poles, you won't need to go deep at all; you could
put some sort of decorative top on:

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