Denise Nickerson, who has died aged 62, was a child actress who was picked, aged 13, to play the part of Violet Beauregarde, the gum-chewing know-it-all who blows up into a blueberry in the quirky 1971 film Willy Wonka & the Chocolate Factory, directed by Mel Stuart and based on Roald Dahl's Charlie & the Chocolate ...