For more than four decades, Mr. Ziegler displayed a restless curiosity with topics ranging from London during the Second World War air raids to the horrors of bubonic plague in medieval Britain and across Europe. Yet his gaze was mainly focused on his homeland and the personalities and institutions that helped shape it.

His own life gave him a foundation in the rarefied worlds he chronicled – as well as the forces that have shaped Britain’s modern identity. Mr. Ziegler attended the elite schools of Eton and Oxford. He then served in the British Foreign Service at a time when Britain’s colonial power was unraveling, returning to Britain on the eve of the social and economic upheavals of the 1960s and 1970s.

“The biographer’s first responsibility is to the truth and to the reader,” Mr. Ziegler said in a 2011 interview. than good will, then he shouldn’t be writing a biography.”

Some of the subjects he researched had built-in name recognition: the Barings banking empire (“The Sixth Great Power”, 1988); the founder of the Rhodes Scholarships (“Legacy: Cecil Rhodes”, 2008); and Lord Louis Mountbatten (‘Mountbatten’, 1985), a member of the royal family and naval officer who was killed in a 1979 bomb attack by the Irish Republican Army.

Other lives he examined were less prominent, but still offered windows into the vanity of Britain’s social swell and blue blood. His 1981 biopic ‘Diana Cooper’ chronicled the life of a seductive aristocrat who inspired author Evelyn Waugh’s character Algernon Stitch in his 1938 satire on journalism, ‘Scoop’.

In 2004, Mr. Ziegler’s “Man of Letters” wrote the maverick British publisher Rupert Hart-Davis, who edited the first edition of Oscar Wilde’s collected letters that shed new light on the libertine writer. Mr. Ziegler’s 1999 biography, “Osbert Sitwell”, visited the life of a minor British poet who rose to greater fame as a magnet for artists and iconoclasts.

“Even after Ziegler decides that ‘Osbert is worth a book,’ he says it’s ‘not so much because of what he did as because of what he was,'” wrote reviewer Adam Kirsch in The Washington Post. “Sitwell himself would have bitterly resented this judgment, but Ziegler shows it to be more or less correct.”

Mr. Ziegler received acclaim from reviewers for his extensive research and reader-friendly stories across more than 20 books. However, some reviewers disagreed with some of Mr. Ziegler for failing to penetrate deeper into the minds and motivations of its subjects.

“Readable and judicious as it is, the book is not without its flaws,” wrote London Observer reviewer Geoffrey Wheatcroft of Mr Ziegler’s 2010 book “Edward Heath” about the British prime minister at a time of labor and economic turmoil in the early seventies. .

Writer Christopher Hitchens lamented “Ziegler’s boring consensus prose” in a review of Ziegler’s 1993 biography “Wilson” about another former British Prime Minister, Harold Wilson.

In many books, the research of Mr. Ziegler himself in connections with the royal family. He became something of an insider for the project about Edward VIII, who in 1936 abdicated the throne instead of ending his relationship with a divorced American woman, Wallis Simpson. His decision divided the nation – love versus duty – and became an open wound within the monarchy as Edward and Simpson went into self-exile in France.

Buckingham Palace had kept its files on Edward and the abdication for scholars and others. In the late 1980s, the Palace was looking for an official biographer and Mr. Zeigler was chosen on the basis of his previous biographies.

It was the first time anyone outside the royal borders had been allowed to look into the archives, which included diaries and correspondence with Queen Mary and Edward’s brother, who became George VI after the abdication. It was critical access, Mr. Ziegler said, to lend credence to the book “King Edward VIII: The Official Biography” (1990).

“Human memory is terrifyingly fallible,” said Mr. Ziegler, “and I’ve learned over the years not to expect precise dates or call recordings when interviewing people who knew my subject.”

A New York Times review of the book asked, “What does an official biographer do with a soap opera subject?”

“If he is Philip Ziegler,” wrote reviewer Zara Steiner, “he makes the story of Edward, Prince of Wales, then King and finally Duke of Windsor, a book of such compelling interest and frankness that it is difficult to to put down. “

If a wealth of material helped expand Edward’s story, the opposite turned out to be true with famed actor Laurence Olivier.

Mr Ziegler said he had stacks of documents and hours of recorded interviews about Olivier’s life, work and loves, including his marriage to actress Vivien Leigh. But Mr. Ziegler felt he could never fully understand Olivier or define the source of his genius on stage and screen.

“He was always acting,” Mr. Ziegler said, and would “remove himself from their discussions.”

“So far I’ve had everyone I’ve written about feel like I was chipping away, poking away, going deeper and deeper and eventually I’d come through to someone real,” Mr Ziegler said in a 2013 book event shortly after the release of “Olivier.”

“With Olivier, I always came out on the other side,” he added, “and I realized I hadn’t managed to commit myself fully.”

Philip Sandeman Ziegler was born on December 24, 1929 in Ringwood, a village in Hampshire, about 10 miles from the English Channel. His father was an army officer and his mother a housewife.

Mr Ziegler served in the British Army during the Second World War and graduated from Oxford’s New College in 1951 with a degree in jurisprudence. The following year he joined the Ministry of Foreign Affairs and held diplomatic posts in Vientiane, Laos; Paris; Pretoria, South Africa and Bogotá.

In 1967, gunmen broke into their Bogotá home and shot dead his wife, Sarah Collins. Mr. Ziegler, who was injured in the attack, resigned from the diplomatic service to take a job with the William Collins publishing house, then run by his father-in-law.

While in the diplomatic corps, Mr. Ziegler tried his hand at a novel. It was “horrible,” he said. He turned to non-fiction. He published his first biography in 1962, “Duchess of Dino”, about Dorothea Courtland, a mistress of the 19th century French diplomat Charles Maurice de Talleyrand. In 1969, the account of Mr. Ziegler on the plague, “The Black Death”, a bestseller despite some medieval scholars considering it lacking in academic depth.

He rose to editor-in-chief at Collins and left in 1980 to focus on writing.

Mr. Ziegler married Mary Clare Charrington in 1971; she died in 2017. Survivors include a son and daughter from his first marriage; and a son from his second.

Mr. Ziegler often described himself as an obsessive researcher. Only a fraction of what he collected made it into print.

“Ideally, the biographer should know everything about his subject and then discard 99 percent of his information, leaving only the essentials,” Ziegler said in 2011. “Obviously, you can never hope to discover something that approaches ‘everything’ , except one can discover much.”