well update is with a chainsaw we managed to get it to about
10cm above ground level.
we have cut a few channells in it to assist rotting the stump out, but it is still above ground level.
the wood is incredibly hard (no pun intended) though and the chainsaw pretty much gave up by the end.
pics to come of the progress, but now to try and get it below the ground level.
the only thing i can think of is to just chip away at the surface with an axe or log splitter but i don't think i am going to get far.