In 1984, due to the zoo's declining attendance, Tussauds's commissioned John Wardley to come up with plans to revitalize the park. Wardley had a huge influence on the rides being created at both Chessington and its sister parks Thorpe Park and Alton Towers. The decision was made to open a theme park to complement the zoo, and so Chessington World of Adventures was born. On 7 July 1987 Chessington World of Adventures opened to the public in a ceremony including HRH Prince Edward. The park was built on a relatively small budget of around £12 million, to test the still-emerging theme park market.