Do you wanna buy a pebble?” A pint-sized girl strides across the beach and fixes me with the kind of stare characteristic of a Marrakesh market stall holder. Bargaining is going to be hard. Our guide, Alison Hurst, introduces us. “This is Shannon, and over there is her friend, Brona,” she says, indicating another girl avidly combing the beach behind us. “Now you’ve met almost half the island’s children.” Rathlin is Northern Ireland’s only inhabited island; with a population of 70 (including five children) this is only just the case.