William Hancock was the son of James Hancock, a cabinetmaker, and Betty Hancock (nee Coleman). He was a member of the Hancock family of Marlborough, England. The Hancocks were a significant British family in the eighteenth and nineteenth centuries, known for their contributions to science, art, and industry.

William Hancock was a cabinetmaker. He set up his cabinet-making and upholstery business in Bury St Edmunds, Suffolk, in 1815. He is best known for making an elm cabinet of ‘superior beauty’ which was presented to George IV in 1825, and remains at Buckingham Palace, and a confidential letter box with secret locking mechanisms for Marquis of Bristol at Ickworth. He also allegedly made the first set of inflatable rubber cushions for the Houses of Parliament between 1834 and 1840. Following financial struggles, he joined his brother, Thomas, at Hancock & Co in Goswell Mews, taking over patent for book-binding 'perfect binding' (soft cover).