Why Kate's copying Diana: Charles failed. So did Camilla. But as the Duchess sets out to conquer New York, she has a secret weapon

For Kate, who will one day inherit Diana's title of Princess of Wales but has yet to acquire her dazzling vitality, the next three days will be her toughest overseas trip yet, writes RICHARD KAY. The Duchess's visit to Los Angeles and Hollywood three years ago (pictured left and top right with Michelle and Barack Obama) was a brilliant success. And by following in the footsteps of Diana in 1989 (second from left) and 1980 (bottom right with Prince Charles and the Reagans), she will give herself the best possible chance of making her visit a success.