Mike wrote ...
I have spent a nice Sunday afternoon cutting down a 3 meter conifer
to ground level and it is not possible to dig out any lower without
digging up the public foot path or my tarmac drive.

What I want to do now is to kill the stump and root system.
The stump is approx. 30cm across.
I hunted around the garage and found a old bottle of SBK,
so I drilled in some holes and poured it in the stump.

What else would help or speed up the process and
how long do you think it will take to die so that it will be easy
to smash the stump out.

I need to extend my path over the top of it eventually.

You already have killed it simply by cutting it down, conifers cannot regrow
from old wood as they do not have dormant buds. Your SBK was wasted.
The stump and roots will gradually rot away over the next few years.

--
Regards
Bob Hobden
17mls W. of London.UK