Nicolson died last Thursday at Sissinghurst Castle, south of London.
The son of the diplomat Harold Nicolson and the writer Vita Sackville-West, Nicolson grew up in the Bloomsbury literary circle and centred much of his literary work on its rarefied atmosphere.
Later in life, he managed Sissinghurst, which had been restored by his parents and now belongs to the National Trust.
In 1973, Nicolson published Portrait of a Marriage, the candid account of his parents’ affectionate 50-year marriage, during which both had several homosexual affairs. He based the book in part on Sackville-West’s written account of her affair with the writer Violet Trefusis. Nicolson had discovered the writings in a locked bag after his mother’s death. He described his parents’ marriage as "the strangest and most successful union that two gifted people have ever enjoyed".
"The marriage succeeded because each found permanent and undiluted happiness only in the company of the other," he wrote. "If their marriage is seen as a harbour, their love affairs were ports of call. It was to the harbour that each returned; it was there that both were based."
Between 1975 and 1980, he edited six volumes of the letters of Virginia Woolf, another of his mother’s lovers. A collection of his parents’ letters followed in 1992, and a one-volume selection from his father’s diaries was published this year.
With George Weidenfeld, he founded the publishing house Weidenfeld and Nicolson in 1948. The firm gained notoriety in 1959 by publishing - against Nicolson’s advice - a British edition of Vladimir Nabokov’s Lolita, despite the threat of prosecution for obscenity.
No legal action was taken and the book’s strong sales put the publishers on a secure financial footing. Nicolson resigned from the company in 1964, but remained a director until 1992.
He was elected to the House of Commons in 1952 as a Conservative, but antagonised his local party association first by supporting legislation to ban the death penalty, and then by rebelling against the Conservative government’s policy over the Suez crisis in 1956. His political career effectively ended in 1959 when he lost a vote of confidence by the local association.
During the Second World War, Nicolson had been part of a British army unit involved in handing over 70,000 anti-Soviet Cossack and Yugoslav prisoners for certain death at the hands of communist forces. In 1989, he was a key witness for Count Nikolai Tolstoy, who was being sued for libel by Lord Aldington. Tolstoy had accused Aldington of organising the betrayal of the Cossacks.
Nicolson testified that British troops had lied to the captives about their destination, and he recalled the Yugoslavs hammering on the inside of their railway carriages, shouting angrily at the British.
"This scene was repeated day after day, twice a day. It was the most horrible experience of my life," Nicolson said.
His biography of Mary Curzon, the American heiress who married Lord Curzon, the British viceroy of India, won the Whitbread prize in 1977.
Other biography subjects included Harold Alexander, the Second World War British commander in the Mediterranean (1973); Virginia Woolf (2000) and Fanny Burney (2002). His autobiography, Long Life, was published in 1997; and in 1986 he collaborated with his son on Two Roads to Dodge City, an account of their separate wanderings in the United States.
He was divorced in 1970 from his wife, Philippa Tennyson d’Eyncourt, who died in 1983. Nicolson is survived by a son and two daughters.