A lifelong friend of 
Mary Russell Mitford
                           who knew her from their childhood in the 1790s, Harness launched the first
                           major effort to collect and edit Mitford’s letters into a series of volumes,
                           which was completed by his assistant, 
Alfred Guy
                                 Kingan L’Estrange a year after Harness’s death, and published
                           as 
The Life of Mary Russell Mitford, Related
                                 in a Selection from her Letters to her Friends. This collection
                           was originally intended to be six volumes, but was cut back to three by the
                           publishers, to Harness’s distress. Harness and 
Byron were also friends from
                           their schooling at Harrow, as Byron sympathized with Harness’s experience of
                           a disabled foot, crushed in an accident in early childhood. Byron considered
                           dedicating 
the first two cantos of Childe Harold’s
                                 Pilgrimage
                               to Harness, but refrained so as not to taint Harness’s reputation as
                           he was taking orders as an Anglican curate. Harness admired and encouraged
                           Mitford’s playwrighting in particular, and she commented that he was one of
                           the few of her friends who thought she should prioritize the drama over
                           prose. When 
William Macready was
                           attacked in 
an anonymous Blackwood’s Magazine piece
                                 in 1825 for his demands and rudeness to Mitford over revisions to
                           
Rienzi, Macready assumed that Harness was
                           the author of the anonymous piece, though in 
1839
                           after many years of distance, Harness assured Macready in person that he was
                           not the writer, though he may have shared word of the poor treatment his
                           friend had endured. William Harness was the son of John
                           Harness, M.D. and Sarah Dredge; he was baptized at Whitchurch, Hampshire on
                           April 13, 1790. He received his B.A. in 1812 and his M.A. in 1816 from
                           Christ’s College, Cambridge. He served as curate at Kelmeston, Hampshire
                           (1812) and Dorking (1814-1816). He was preacher at Trinity Chapel, Conduit
                           Street, London and minister and lecturer at St. Anne’s in Soho. He was Boyle
                           lecturer in London (1822) and was curate at Hampstead from 1828 to 1844. In
                           1825, he published an eight-volume edition of Shakespeare, including a
                           biography; his friends would later endow a prize in his name at Cambridge
                           for the study of Shakespearean literature. He also authored numerous essays
                           and reviews, some for the 
Quarterly Review. From 1844 to 1847 he was
                           minister of Brompton Chapel in London. He undertook to raise the funds to
                           build the church of All Saints, Knightsbridge, in the parish of St.
                           Margaret’s Westminster, which opened in 1849, and he then became perpetual curate
                           of
                           that congregation. At the 1851 and 1861 censuses, he lived at 3 Hyde Park
                           Terrace, Westminster St. Margaret, Middlesex, with his sister 
Mary Harness
                           and his first cousin 
Jemima Harness, daughter of his uncle William. He died
                           while on a visit to one of his former curates in
                           Battle, Sussex. At the time of his death he living at the same address at 3
                           Hyde Park Terrace; he is buried in Bath.Sources: 
                              Duncan-Jones, Miss Mitford and Mr. Harness
                              (1955); Lord Byron and His Times: