From the 1830s, the British landscape was transformed by the development of the steam-hauled railway system, which necessitated bridges, viaducts and tunnels. Of such structures, tunnel entrances feature little in serious studies of railway architecture. However, rich archival evidence exists relating to the designs of Isambard Kingdom Brunel for the tunnel portals on the Great Western Railway between London and Bristol, including numerous pencil and ink drawings in sketchbooks held by the Brunel Archive, University of Bristol, and watercolour elevations in the Network Rail Archive in York, as well as lithographs of the portals by John Cooke Bourne for his History and Description of the Great Western Railway (1846). Brunel's drawings, unique among nineteenth-century engineers, range from the classical style for Box and Middle Hill tunnels in Wiltshire, through the Gothic for Twerton in Somerset, to the Romanesque for Brislington on the edge of Bristol, his so-called ‘Tunnel No. 1’. In their variety and careful design, Brunel's portals represent an important part of Britain's railway and industrial architectural heritage.