British Prime Minister Boris Johnson has delivered the most substantial alteration of European politics in decades, as a lifetime of jousting with defenders of the European Union culminated on Friday in an exit from the political bloc.

“Brexit is actually the single biggest event in British history since the end of World War II,” Nile Gardiner, a former Margaret Thatcher aide and expert on U.S.-U.K. relations at the Heritage Foundation, told the Washington Examiner. “It’s a huge game changer, not only for the U.K. but also for Europe as well. And I think that most Britons are embracing a future outside the EU.”