Say what you like about the British royal family and their fashion sense; as Helen Mirren observed of Queen Elizabeth II’s hairstyle in her Oscar acceptance speech last year, when they find a look they like, they stick with it. The Queen’s mother, for example, never stopped dressing like it was 1936, a feat she was able to pull off with some panache thanks to Norman Hartnell, her official dressmaker and a onetime major force in English fashion. Hartnell is the subject of a new book, “Be Dazzled! Norman Hartnell: Sixty Years of Glamour and Fashion” (Pointed Leaf Press), that’s lavishly illustrated with the evening gowns and court attire he was famous for. Though he was still designing at his death in 1979, Sir Norman’s designs (he was knighted in 1977) always suggested a ballroom in Mayfair sometime in the pre-war years. Like the royals he dressed, he knew what he liked.