The Life and Works of John Rennie (7 June 1761 – 4 October 1821)

Kennet & Avon Canal - Overview

Sue Threader

By 1723, the small river Kennet which joined the Thames near Reading, had been made navigable upstream to Newbury. Five years later, the Bristol Avon was canalised from Hanham Mills – its tidal limit – as far as Bath. These developments raised the possibility of joining the two navigable rivers by means of a canal section to establish a navigable inland route between Bristol and London to avoid a sea voyage around the tip of Cornwall, although it was not until the late 1780s that plans to create what became the Kennet and Avon Canal began to develop in earnest and a committee was formed to survey a route for the canal. The initial proposal on a circuitous route was regarded as too expensive and there were doubts about the sufficiency of the water supply. In 1793 steps were taken to appoint a new engineer and the committee chose John Rennie who proposed a more direct route through Devizes, Trowbridge and Newbury.

Rennie’s route was shorter but necessitated building a system of locks to climb the very steep Caen Hill and a pair of sizeable aqueducts which he conceived on a resplendent scale, in a style that shows all his characteristic design-flair. The canal opened in 1810 after 16 years of construction, including the building of many locks and small bridges. The spectacular flight of 16 Caen Hill Locks was the last part of Rennie’s scheme to be completed.

The Kennet and Avon is a broad canal, varying from 40ft to 44ft in width and nominally 5ft deep. The canal section is 57 miles (91km) long, joining River Avon at Bath, via Devizes and Hungerford, to River Kennet at Newbury. It rises 404ft 6ins from Bath to the summit level 15 miles away and 450ft above sea level; then falls 210ft to Newbury. There are 79 locks, five masonry aqueducts (four original, one added later) and three tunnels. The Bruce Tunnel – a Rennie design – is over 500 ft. long and is the canal tunnel with the second largest cross-sectional area of any remaining open to navigation in Britain. Numerous overbridges were built in stone, brick, cast-iron and timber as well as three pumping stations at Claverton and Crofton as well as wharves and depots at Bradford-on-Avon. Nine hand-operated timber swing bridges were built to Rennie’s designs, each with ball-bearing pivots.

The Kennet and Avon was joined near Limpley Stoke by the Somerset Coal Canal (1801) and the Wilts and Berks Canal (1810), traces of which have now almost disappeared. At first highly profitable, the opening of the Great Western Railway in 1841 caused a rapid decline in the canal’s fortunes and traffic declined until by the end of the nineteenth century through traffic had ceased and the canal eventually fell into disuse. In recent years the Kennet and Avon Canal Trust, in cooperation with the British Waterways Board and Canal and River Trust have carried out considerable restoration work and the route is again navigable.