Former Secretary of Defense Donald Rumsfeld on Tuesday spoke in conversation at The Heritage Foundation with Heritage President Edwin J. Feulner about his long career in public service and private enterprise and on his recently published and best-selling memoir Known and Unknown.

The memoir is a fascinating read, as reviewers both friendly and hostile have agreed. As the Secretary has been alive for one-third of the history of the United States—as he ruefully observed—it’s not surprising that his memoir is such a treasure trove. His remarks on Ronald Reagan, Margaret Thatcher, and the Law of the Sea Treaty are a relevant example. In 1982, Rumsfeld was asked to serve as President Reagan’s emissary on the treaty. As he records:

The so-called United Nations Convention on the Law of the Sea was designed to codify navigation rights in international waters. But it had grown into something considerably more ambitious, with a proviso that would put all natural resources found in the seabeds of international waters … into the hands of what was ominously called the International Seabed Authority.

The State Department bureaucracy was thoroughly in favor of the treaty, but Reagan wasn’t. His willingness to overturn that consensus told Rumsfeld that “we had a vastly different president in the White House.” Reagan gave Rumsfeld ambassadorial status and ordered him to rally support for the new U.S. position with key foreign leaders.

This wasn’t an easy job. As Rumsfeld notes, thanks to the previous failure of U.S. leadership, all the momentum was moving in the other direction. In socialist-led France, Rumsfeld got a cold welcome. But in Britain, Margaret Thatcher was Prime Minister. Her exchange with Rumsfeld was brisk:

“Mr. Ambassador, if I understand correctly, what this Law of the Sea Treaty proposes is nothing less than the international nationalization of roughly two thirds of the Earth’s surface,” she began. “And you know how I feel about nationalization.” “I do indeed, Prime Minister,” I responded. Mrs. Thatcher had made transferring nationalized businesses, from utilities to mining companies, back to the private sector a hallmark of her premiership. She smiled. “Tell Ronnie I’m with him.”

The Law of the Sea Treaty is still out there, still ratified by the United States Senate, and still deeply flawed. Thanks to Secretary Rumsfeld for reminding us, yet again, that Reagan opposed it and for the insight into the close Anglo–American relationship that flourished under Ronald Reagan and Margaret Thatcher.