Lord Carrington, a versatile British politician who held senior posts under Conservative prime ministers from Winston Churchill to Margaret Thatcher and who was secretary general of NATO in the last years of the Cold War, died on Monday. He was 99.

His death was confirmed by Prime Minister Theresa May. She did not say where he died.

The best-remembered act of Lord Carrington’s long political career was a resignation. His decision in 1982 to step down as foreign secretary, because he had failed to anticipate what he described as the “humiliating affront” of Argentina’s invasion of the Falkland Islands, is frequently cited as a rare example of an honorable ministerial departure.

Lord Carrington, the sixth baron of Carrington, was the longest-serving member of the House of Lords and a descendant of textile merchants, bankers and members of Parliament dating to the 18th century. He attended Eton and Sandhurst, was a decorated officer in World War II and could have spent the rest of his days in baronial splendor on his family’s Buckinghamshire estate.

Instead, he plunged into postwar politics, diplomacy and public service. In a career that spanned nearly five decades, Lord Carrington was parliamentary secretary of agriculture, first lord of the Admiralty and, in a succession of cabinet posts, secretary of defense, energy and foreign affairs.