Roald Dahl on 13 September is celebrated as "Roald Dahl Day" in Africa, the United Kingdom and Latin America. In honour of Dahl, the Royal Gibraltar Post Office issued a set of four stamps in 2010 featuring Quentin Blake's original illustrations for four of the children's books written by Dahl during his long career; "The BFG", "The Twits", "Charlie and the Chocolate Factory", and "Matilda". A set of six stamps was issued by Royal Mail in 2012, featuring Blake's illustrations for "Charlie and the Chocolate Factory", "The Twits", "The Witches", "Matilda", "Fantastic Mr Fox", and "James and the Giant Peach". Dahl's influence
Roald Dahl Theo Dahl was severely injured when his baby carriage was struck by a taxicab in New York City. For a time, he suffered from hydrocephalus. As a result, his father became involved in the development of what became known as the "Wade-Dahl-Till" (or WDT) valve, a device to alleviate the condition. The valve was a collaboration between Dahl, hydraulic engineer Stanley Wade, and London's Great Ormond Street Hospital neurosurgeon Kenneth Till, and was used successfully on almost 3,000 children around the world. In November 1962, Dahl's daughter Olivia died of measles encephalitis, age seven. Her death left Dahl "limp with