There was a time when no monarch worthy of his ermine considered a throne worth sitting on unless its perquisites included a private yacht. But no more. Frederika of Greece, whose royal veins course with the blood of a host of Europe's kingly houses, has a throne but no yacht. Most of her royal cousins have neither. Then Frederika got an idea: she and her husband, King Paul, would play hosts to their less fortunate relatives aboard Greece's brand-new 5,500-ton liner Agamemnon. Gratefully, the members of Europe's royal families swept aboard the ship at Naples.
Numbering nearly 90 in all,...