The founder of scientific art criticism, Wornum was born in Thornton, near Norham in Northumberland, the son of the piano manufacturer, Robert Wornum (1780-1852), the inventor of the now universally used upright action for the piano. He studied at London University in 1832 and then trained as a painter. In 1846, he began writing in the Art Union and in 1848, was appointed lecturer on art to the government schools of design. He compiled the official catalogue of the National Gallery in 1847 and in 1854 was made keeper and secretary of the gallery. He was a friend of John Ruskin and in 1861 he was chiefly responsible for obtaining the restoration of Turner collections to the National Gallery in 1860-61.His writings include Epochs of Painting (1847) and Analysis of Ornament (1856), which long served as the basic textbook on its subject, reaching its eighth edition in 1893.