The first of 12 days of
Pottermore teasers leading up to the release of
Harry Potter and the Half-Blood Prince gave a short preview of the town of Cokeworth, where Lily and Petunia Evans grew up, nearby Severus Snape, written by J.K. Rowling. It was also the same town that the Dursleys ran to in order to escape from Harry's Hogwarts letters in
Philosopher's/Sorcerer's Stone.
“Perhaps Uncle Vernon has a vague idea that Cokeworth is so distinctly unmagical, the letters will not follow them there. He ought to have known better; after all Petunia’s sister, Lily, turned into a talented witch in Cokeworth.”