If you cut them to the ground and apply (paint) 'stump killer' to each stump within 48 hours and cover them.

Chop them down as close to the ground as possible. Now you need a medium wood bit and a drill - drill into the stumps to make holes, but not right through the whole thing. Fill up the holes with SBK brushwood killer (don't spill it on the ground) and cover with something. Drilling the holes means the treatment penetrates the woody tissue more efficiently. If it's a large stump, put a ring of holes about half an inch in from the bark or outside of the stump all round.