This article is not part of the Harry Potter universe. This article covers a subject that is part of the real world, and thus should not be taken as a part of the Harry Potter universe.
William started playing the role as 'Boy Next Door' in William and Mary [Episode #2.2 #2.4], then he became famous. Later, in 2004, he played the Young Rawdy Crawley in Vanity Fair. He then appeared as Nigel Wolpert in the Harry Potter films.