It looks easy on YouTube but after I had wasted half a length of cornice cutting the wrong angles, I called in the experts, Stewart's Interior Linings. Greg Stewart sent one of his men, young Brett, who had the whole thing done in an hour.
He then headed off to the Snowies for a spot of deer-hunting. I gave him a bottle of Jägermeister to show my appreciation for a job well done and to keep him warm in the mountains.