While I was tempted to take the cowardly way out, my inner Scappy Do took over.
So I backpedled through various enviornments firing at range and dropped a fireball scroll on him when he started to wear me down so my dragon stone is just waiting for the quest.A useful lesson from other people's experience is that if you want acheivement, play online. I am not sure I do but have a tendancy to try to fix any bug I encounter.