Fence Posts - Boring

I have an old and very thick row of Leylandii that I want to replace with a close boarded fence. I can't remove the tree roots due to drives on both sides, so I plan to saw them off at ground level.

My problem is how to bore holes for the fence posts. This means drilling through Leylandii stumps and thick roots. A normal post hole borer would be useless. Any kind of auger is likely to just jam round the roots. Any ideas?

I have just removed 15 of these monsters. I used a thin heavy duty spade end welded to a 5 foot scaffold pole. I kept the end sharpened and they worked through the roots with several heavy blows. The narrowness of the blade kept the post holes reasonably sized.

When I went to collect the posts and panels, bu gg er me but there were similar tools being sold by the company. Slightly lighter but far better machined than mine.

TT

Could you chop the trees down to 6' high and remove any remaining branches, then run the rails between the trunks and board as usual? You would have possibly the stoutest fence posts ever!