William P. Clark, a former national security adviser to President Ronald Reagan and Interior secretary, has died after a battle with Parkinson’s disease. He was 81. Clark, a former California Supreme Court judge, became one of Reagan’s most trusted confidants, serving as deputy secretary of state (1981-1982), national security adviser (1982-1983), and Interior secretary (1983-1985)... Added Faith Whittlesey, former Reagan adviser and ambassador to Switzerland: “Bill Clark was Ronald Reagan’s best friend and was the great unsung hero of the Cold War. He faithfully and effectively carried out Ronald Reagan’s policies within the government in the face of constant opposition...