Harvard Business School professor Debora L. Spar writes, on page 33 of her book Ruling the Waves:
Henry [The Navigator] returned from Africa eager to crusade again, and to capture the nearby island of Gibraltar. But his father refused permission …
Well, if I were King of Portugal and my son came to me seeking to conquer the island of Gibraltar, I’d refuse permission, too, at least until he’d done his homework. There is a Gibraltar Island, but it’s on Lake Erie; to the best of my knowledge, the promontory at the southern end of Spain is not and has never been an island. The book has a good reputation, is widely cited, and has been on my to-read list for years, but I always worry when I see this kind of failed reality check.