Born at Sprowston, Norfolk of Methodist parentage, he was articled at 17 to a solicitor in Norwich and qualified as an attorney in 1829. In 1842 he inherited Letheringsett Hall from a uncle, William Hardy, on condition that he added 'Hardy' to his surname. He was prominent in local government and for many years was the only nonconformist JP in Norfolk. A staunch supporter of the Reform movement, he argued the case of the three ministers expelled by the WM Conference in 1849 and was himself expelled by a WM District Meeting in 1850. Controversy between the Conference and the Reform party in Holt over responsibility for chapel debts led to a court case won by the latter. In 1863 he built an impressive Gothic chapel for the UMFC on Obelisk Plain, which survives as the present Methodist church. He died at Letheringsett early in 1895.
Of his nine children one daughter married the Norwich MP, Jeremiah James Colman (of 'Colman's Mustard' fame). One son, Herbert Hardy Cozens-Hardy (1838-1920), 1st Baron Cozens-Hardy of Letheringsett, was the Liberal MP for North Norfolk 1885-1899. He then became Lord Justice of Appeal and Master of the Rolls and was raied to the peeraage in 1914. He was the father-in-law of the Congregational minister C. Sylvester Horne, minister of Whitefield's Tabernacle in Tottenham Court Road and author of HP 244 and 435.