Three of us are sitting at the kitchen table at Billy and Isobel Muir’s farmhouse on North Ronaldsay: Robert, the photographer, me, and Billy. Isobel is making lunch. Or she’s trying to make lunch, but Billy keeps getting up and down to look for things, shifting the framed pictures of grandchildren from the mantelpiece, moving the Herd Register For Female Bovine Animals three inches to the left. He’s grumbling under his breath.