On a summer day nearly twelve hundred years ago, three ships with bright red sails drew near to one of the little ports of the Dorset coast in the south of England.

The townsfolk saw the ships, and paying no heed to the bright sails, said carelessly one to another, 'The merchantmen will be in port to-day.' And the harbour-master gathered together a few of his men and hastened to the quay. For he, too, had seen the ships, and, as in duty bound, he went to meet them, to demand from the captains the port taxes which were lawfully due to the king.

But townsfolk and harbour-master alike had made a grievous mistake that summer day. For, as they soon discovered to their cost, and as the red sails might have forewarned them, the three ships were no peaceful merchantmen...