Tim Watts wrote:
I have a 6" stump left from a tree I just chopped down (threatening to break
the drain chamber in my garden that's all of a foot away from the trunk).

No idea what the tree was, but I need to ensure its complete and permanent
demise.

Apart from the old drill-holes-in-stump and pour in diesel/old-sump-oil
trick (don't have any mouldy sump oil to hand anyway) what would be a good
product to use?

Sulphuric acid. (Battery acid.)

--
Rusty