This wasn't a walk, but I was reminded of the incident when I read someone's post in the Wild Camping Petition thread, where he referred to people pulling off the road in their camper van and pitching their family sized frame tents.
Well, many many years ago we toured Scotland in a VW camper van, and took it across to Mull on the ferry. We liked it so much there we decided to spend the night and return to the mainland the following day. I don't know what it's like now, but there were no camp sites on the island then. We pulled off a single track road that had grass growing along the middle, near the brow of a hill where there was a lovely patch of level grass in the bracken, and a stream with a pretty waterfall behind. We pitched our large ridge tent on the grass, and enjoyed a peaceful night.
In the sunny morning, my wife, 22 then, wandered over to the stream for a wash, asking me to shout if I heard a car coming (there was only about three passed us the whole time we were there). Sitting in a folding chair reading an old newspaper, I looked up after a while and there was an old man quietly wheeling his bicycle up the hill. Too late to warn my wife, I looked round to see her standing splashing about in the stream without a stitch on.
The old fellow's gaze followed mine, and, spotting my naked wife, his jaw dropped, then he jumped on his bike and pedalled away as fast as he could! That was one of a few times I've come close to being divorced!