right|thumb|William Hayley by Henry Howard
William Hayley (9 November 174512 November 1820) was an English writer, best known as the biographer of his friend William Cowper.
Biography
thumb|130px|Plaque at site of Hayley's home in Felpham, Sussex
thumb|130px|Plaque at site of Hayley's home in Eartham, Sussex
Born at Chichester, he was sent to Eton in 1757, and to Trinity Hall, Cambridge, in 1762; his connection with the Middle Temple, London, where he was admitted in 1766, was merely nominal. In 1767 he left Cambridge and went to live in London. His private means enabled Hayley to live on his patrimonial estate at Eartham, Sussex, and he retired there in 1774. The location of this house in Eartham is now occupied by the Great Ballard School.
thumb|left|120px|Hayley's son, Thomas Alphonso. ([[Jeremiah Meyer)]]So great was Hayley's fame that on Thomas Warton's death in 1790 he was offered the laureateship, which he refused. In 1792, while writing the Life of Milton, Hayley made Cowper's acquaintance. A warm friendship sprang up between the two which lasted till Cowper's death in 1800. Hayley indeed was mainly instrumental in getting Cowper his pension. In 1800 Hayley also lost his natural son, Thomas Alphonso Hayley, to whom he was devotedly attached. He had been a pupil of John Flaxman's, to whom Hayley's Essay on Sculpture (1800) is addressed. Flaxman introduced William Blake to Hayley, and after the latter had moved in 1800 to his marine hermitage at Felpham, Sussex. Blake settled near him for three years to engrave the illustrations for the Life of Cowper. This, Hayley's best known work, was published in 1803–1804 (Chichester) in 5 vols.
It was appropriate that the gallery's new wing is situated on 8 North Pallant, which formed part of the house in which Hayley was born. A portrait of Hayley by George Romney is currently on long-term display in the gallery.
Family
In 1769 Hayley married Eliza Ball (1750-1797), daughter of Thomas Ball, dean of Chichester. Eliza Ball Hayley was a translator and an essayist. She translated into English two essays by the French essayist Anna Thèrese de Lambert (1647 – 1733), Traité de l’Amitié (1732) and Traité de la Vieillesse (1732), published in 1780 as Essays on Friendship and Old Age by the Marchioness de Lambert. Sixteen years later she published an original essay, The Triumph of Acquaintance over Friendship: an Essay for the Times (1796). She died in 1797; after being separated from William since 1789. He attributed the mental illness she suffered as reasoning for the separation. He married in 1809 Mary Welford, but they also separated after three years. He left no child.