Prime Minister May’s Lancaster House speech outlining the British government’s Brexit agenda takes an impressive step forward in Britain’s withdrawal from the European Union — and keeps a weather eye out for the man who is about to become President Trump. Brexit was “a vote to restore . . . our parliamentary democracy, national self-determination, and to become even more global and internationalist in action and in spirit.”

The Prime Minister opened with an apologia, setting out the reasons for Britons’ June decision to leave the EU and set out once more on their historic path of international engagement. “The decision to leave the EU represents no desire to become more distant to you, our friends and neighbours,” Mrs. May assured. “It was no attempt to do harm to the EU itself or to any of its remaining member states.” The lovelorn will recognize the “it’s not you, it’s us.”

Mrs. May detailed a dozen markers that will guide her Brexit strategy, from negotiating a new free trade agreement with the Union (maintaining and revising those current provisions that work for both parties) to normalizing relations for EU citizens living and working in the UK (and vice-versa), while assuring member countries of Britain’s continuing commitment to mutually beneficial co-operation in matters of continental security, defence, and cultural engagement.

Europe was not Mrs. May’s only audience. While England is the dominant “kingdom” in the Union, the Prime Minister assured the administrations of Scotland, Wales, and Northern Ireland that their concerns and suggestions will be heard at Westminster. Strengthening “the precious union between the four nations of the United Kingdom” is also part of the Brexit framework, as the referendum vote demonstrated the urban-rural divide and the tensions between England and the periphery regions.

Mrs. May sought to placate Parliament, too. While the government’s Brexit strategy will be “debated and discussed at length,” national self-interest and discipline demand that tactics remain the purview of the negotiating team. Mrs. May confirms “that the government will put the final deal that is agreed between the UK and the EU to a vote in both Houses of Parliament.”

American observers will see the “Trump effect” at work in Mrs. May’s Brexit outline; it may be more accurate to trace this rise in patriotism to Reagan and Thatcher, who battled economic ennui and sclerotic statism in the 1980s and who today inspire millions of Americans, Britons, Europeans in the battle for personal and national sovereignty.

Even within the Brexit camp the war of ideas wages on. Defenders of individual liberty are fear that powers returning to Britain from Brussels are being relegated to home-grown bureaucracies and not to the people to whom they were granted by God. That the power to reverse this “upward” trend remains at the ballot box, and not at the whim of foreign jurisdictions, is no small consolation.

Moreover, Mrs. May’s advocacy of a “modern industrial strategy” conjures corporate cronyism and “picking winners and losers,” akin to President-elect Trump’s own threat of 35% tariffs to keep indigenous industry at home. Far better to look to future prospects than past accomplishment and base economic policy on the pillars of property, competition, innovation, and entrepreneurship.

“Trade is not a zero sum game,” Mrs. May declared. “Free trade between Britain and the European Union means more trade, and more trade means more jobs and more wealth creation. The erection of new barriers to trade, meanwhile means the reverse: less trade, fewer jobs, lower growth.” She addresses not only EU ministers who want “a punitive deal that punishes Britain” but also a Trump administration with protectionist proclivities. Regardless, “it is time for Britain to get out into the world and rediscover its role as a great, global, trading nation.”

America is part of that “Global Britain” plan, with joint representatives mapping the contours of an American-British trade deal once Britain is freed of its European fetters. Happily for the Conservative government, and Mr. Trump has pledged to put Britain at the front of the line for upcoming trade agreements.

Apart from contemporary similarities with President-elect Trump, Theresa May’s Brexit speech raises echoes of another British prime minister and another speech for British independence thirty years ago: Margaret Thatcher’s justly famous “Bruges speech,” where she exclaimed that “We have not successfully rolled back the frontiers of the state in Britain, only to see them re-imposed at a European level with a European super-state exercising a new dominance from Brussels.” Let us hope that Lancaster House proves to be Mrs. May’s own “Iron Lady” moment.

Mr. MacLean maintains the weblog The Organic Tory.