Acton was born into a prominent Anglo-Italian family in Villa La Pietra, his family's estate near Florence, Italy. He claimed that his great-great-grandfather was Commodore Sir John Acton, who was prime minister of Naples under Ferdinand IV, and grandfather of the Roman Catholic historian John Acton. However, the basis of this has been disputed. Harold was in fact the great-great grandson of Sir John's younger brother Joseph Acton (1 Oct 1737-12 Jan 1830) via his eldest son Charles.

His father was the art collector and dealer Arthur Acton (1873-1953), his mother Hortense Mitchell (1871-1962), heiress to a prominent Chicago banking family. The Mitchell fortune allowed Arthur to buy the remarkable Villa La Pietra on the hills of Florence, where Harold lived for much of his life. The only modern furniture in the villa was in the nurseries, and that was disposed of when the children got older (Harold's younger brother William was born in 1906).

His early schooling was at Miss Penrose's private school in Florence. In 1913 his parents sent him to Wixenford preparatory school near Reading in southern England, where Kenneth Clark was a fellow-pupil. By 1916 submarine attacks on shipping had made the journey to England unsafe and so Harold and his brother were sent in September to Chateau de Lancy, an international school near Geneva. In the autumn of 1917 he went to a 'crammer' at Ashlawn in Kent, in order to be prepared for Eton, which he entered on 1 May 1918. Among his contemporaries at Eton were Eric Blair (the writer George Orwell), Cyril Connolly, Robert Byron, Alec Douglas-Home, Ian Fleming, Brian Howard, Oliver Messel, Anthony Powell, Henry Yorke (the novelist Henry Green).

In October 1923 Harold went up to Oxford to read Modern Greats at Christ Church. It was from the balcony of his rooms in Meadow Buildings that he declaimed passages from The Waste Land through a megaphone, an episode recalled in Brideshead Revisited which Waugh gives to the character of Anthony Blanche. While at Oxford he co-founded the avant garde magazine The Oxford Broom, and published his first book of poems, Aquarium (1923).

Unabashedly gay, while at Oxford he was briefly a passionate admirer of, but is not thought to have had an affair with, Evelyn Waugh who dedicated his first novel, Decline and Fall, to him. After leaving Oxford Acton taught in China for several years before returning to England at the outbreak of the Second World War during which he served in RAF intelligence. For the last 25 years of Acton's life, his companion was German-born photographer and artist Alexander Zielcke.[1]

Acton's own works include The Last Medici, Memoirs of an Aesthete and The Bourbons of Naples, a gossipy but well-researched 2 volume history of the Bourbon rulers of the Kingdom of Naples in the 18th and early 19th centuries. He also wrote Peonies and Ponies, an affectionately satirical book about the clash between European and Chinese culture.

In 1974 he was named a Knight Commander of the British Empire (KBE). When he died he left Villa La Pietra to New York University.

Following Acton's death at the age of 89, DNA testing revealed the existence of an illegitimate half-sister, whose heirs have gone to court to challenge Acton's $500 million bequest to New York University.

Acton was buried beside his parents and brother in the Roman Catholic section of the Cimitero Evangelico degli Allori in the suburb of Florence, Galluzzo (Italy).

Published works

• Aquarium, London, Duckworth, 1923
• An Indian Ass, London, Duckworth, 1925.
• Five Saints and an Appendix, London, Holden, 1927.
• Cornelian, London, The Westminster Press, 1928.
• Humdrum, London, The Westminster Press, 1928.
• The Last of the Medici, Florence, G. Orioli, 1930.
• This Chaos, Paris, Hours Press, 1930.
• The Last Medici, London, Faber & Faner, 1932.
• Modern Chinese Poetry (with Ch'en Shih-Hsiang), Duckworth, 1936.
• Famous Chinese Plays (with L.C. Arlington), Peiping, Henri Vetch, 1937.
• Glue and Lacquer: Four Cautionary Tales (with Lee Yi-Hsieh), London, The Golden Cockerel Press, 1941.
• Peonies and Ponies, London, Chatto & Windus, 1941.
• Memoirs of an Aesthete, London, Methuen, 1948.
• Prince Isidore, London, Methuen, 1950.
• The Bourbons of Naples (1734-1825), London, Methuen, 1956.
• Ferdinando Galiani, Rome, Edizioni di Storia e di Letteratura, 1960.
• Florence (with Martin Huerlimann), London, Thames & Hudson, 1960.
• The Last Bourbons of Naples (1825-1861), London, Methuen, 1961.
• Old Lamps for New, London, Methuen, 1965.
• More Memoirs of an Aesthete, London, Methuen, 1970.
• Tit for Tat, London, Hamish Hamilton, 1972.
• Tuscan Villas, London, Thames & Hudson, 1973.
• Nancy Mitford: a Memoir, London, Hamish Hamilton, 1975.
• The Peach Blossom Fan (with Ch'en Shih-Hsiang), Berkeley, University of California Press, 1976.
• The Pazzi Conspiracy, London, Thames & Hudson, 1979.
• The Soul's Gymnasium, London, Hamish Hamilton, 1982.
• Three Extraordinary Ambassadors, London, Thames & Hudson, 1984.
• Florence: a Travellers' Companion (introduction; text ed Edward Chaney), London, Constable, 1986.