Havell was the son of a Reading drawing-master, and he participated in several sketching societies in the early 19th century. In 1805 he contributed to the first exhibition held by the Society of Painters in Water-colours, of which he was a founder-member. At the same time he began to establish himself as an oil painter, in the manner of Richard Wilson and J. M. W. Turner, exhibiting at the Royal Academy and the British Institution.
Initial success was followed by mounting criticism of his idealized treatment of brightly sunlit subjects. The disillusioned Havell accepted the post of official artist to the embassy of China led by William Pitt, Earl Amherst of Arracan (1773–1857), which set out in 1816; Havell was able to sketch the Chinese countryside as the embassy took the return route overland from Beijing to Guangzhou.
From there he moved to India and Ceylon (now Sri Lanka), where he spent six years painting portraits and landscapes before returning to England in 1826. In 1828–9 he travelled in Italy. Subsequently he remained in England, exhibiting vivid landscapes that did not bring him the renown that he had once seemed likely to achieve.
In the late 1830s Havell experimented with ‘photogeny’ (together with his brother Frederick James) and incurred the hostile rivalry of Henry Fox Talbot. A number of his works were engraved, notably a Series of Picturesque Views of the River Thames, reproduced in coloured aquatint in 1811 by his uncle Robert Havell; the latter also published a Series of Picturesque Views of Noblemen’s Seats (1814–23), to which William contributed.
Ashmolean Museum, Christchurch Art Gallery, Courtauld Institute of Art, Hong Kong Museum of Art, National Maritime Museum, Tate Gallery, Tyne & Wear Museum.