When Captain Roger Angmering built himself a house in the year 1782 on the island off Leathercombe Bay, it was thought the height of eccentricity on his part. A man of good family such as he was should have had a decorous mansion set in wide meadows with, perhaps, a running stream and good pasture.

But Captain Roger Angmering had only one great love, the sea. So he built his house-a sturdy house too, as it needed to be, on the little windswept gull-haunted promontory-cut off from land at each high tide…