Answer: United Kingdom
Notes: The United Kingdom houses the headquarters of the "Association of Tennis Professionals". The Association of Tennis Professionals (ATP) is the governing body of the men's professional tennis circuits - the ATP Tour, the ATP Challenger Tour and the ATP Champions Tour. It was formed in September 1972 by Donald Dell, Jack Kramer, and Cliff Drysdale to protect the interests of professional tennis players. Since 1990, the association has organized the ATP Tour, the worldwide tennis tour for men and linked the title of the tour with the organization's name. It is the governing body of men's professional tennis.
