After ploughing through a cave with a bunch of gnomes, I came out onto a ledge and saw another ledge facing me across a chasm. I had a Levitation scroll, so levitated across. Found good stuff at a grave, including a Fine Sword. But there was no ways off the ledge.

I had blown my only Levitation spell. Rather than come back another time, I tried various options for jumping off. Finally found a place that worked: facing the back of the ledge, go as far back and right as you can. Looking down you can see a cliff face that is a bit sloping. Jump off towards it, and you land (with Acrobatics) quite gently on the path from the beach you were on in the Prologue.

Wonderful! Thanks for making it possible, PB.