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

Kennet & Avon Canal - Crofton Beam Engines

Peter Turvey & Ian Broom

The Grade-1 listed summit pumping station at Crofton on the Kennet & Avon Canal dates from 1807-9 and is a unique survivor of a once-common feature of English canals. The site is a miniature industrial community, including workers’ cottages, a smithy for engine and canal maintenance and boiler feed water header pond.

Rennie’s Site Plan 1807 based on Boulton and Watt archives MS/3147/5/608

Not only does the engine house with its boiler house and water supply system survive largely as laid out by Rennie, it also contains one of its two original Boulton and Watt steam engines in full working order. Although modified in the 1840s to improve its efficiency, much of the engine is original. Regularly demonstrated by dedicated volunteers during the summer months, this surviving engine was at work by 1812 and is the oldest in the world still in its original engine house and capable of doing its original job of pumping one tonne of water into the canal on each power stroke.

Rennie had been Boulton & Watt’s London agent before setting up his own engineering consultancy business and was familiar with the use of steam power. However, a steam pumping station to supply the canal summit with water was not part of his original 1794 design for the Canal, He had eliminated the need for pumping by incorporating a 4 km (2 ½ mile) long tunnel to keep the canal at the level of the highest natural water supplies at Crofton. Rennie’s design was sound but expensive. The eminent engineer William Jessop was asked to review the scheme; one of the cost-saving proposals he made was eliminating the tunnel by raising the summit level through short flights of locks at Crofton and Wootton Rivers, and using a steam pumping engine to supply the summit. Jessop estimated that this would save £31,000 – a considerable sum in 1795 – and two years’ work. His proposals for this and other modifications to the canal were adopted.

Crofton Pumping Station, Canal Engine Pound and Lock 60 from the air

In September 1802 Rennie had bought a 36” cylinder Boulton & Watt engine, built in 1801 for the West India Dock Company but never used by them. In June 1807 Rennie reported that ‘the place for the engine house had been marked out and that the tunnels and shafts (to connect with the canal and water supplies) were now proceeding’. He prepared a drawing of the site and sent it to Boulton & Watt on 25 June with a request to send ‘the plan for the double engine house as they wish much to sink the shaft and begin the building’.

The engine house was nearly finished by April 1808 and in May, Thomas Pearson, Boulton & Watt’s engine erector arrived. The engine was at work by the spring of 1809 and the Canal opened in 1810. Rennie’s plan was for two engines, and at the end of 1809 the Canal Committee decided to order a second, larger and more powerful engine to complete the scheme. This engine, of 42” cylinder was ordered in January 1810 and incorporated a major design improvement – a cast iron beam instead of a wooden one. It took a while to install, key parts were still being ordered in October 1811, but were at work by 1812. Unfortunately the Canal Company was not quick to settle Boulton & Watt’s bills, who were not fully paid until January 1813.

The subsequent history of Crofton Pumping station is one of repairs, maintenance and modernisation. By the 1840s the Kennet & Avon Canal was suffering from competition from the newly-opened Great Western railway. Pumping at Crofton was a large cost, and the station was updated adopting the latest, high pressure steam engine technology from Cornwall, where engineers had developed highly efficient engines for mine pumping. In 1844-5 the 1812 engine was modified by the Cornish engineering firm Harveys of Hayle with many new parts and high-pressure steam boilers, raising the steam pressure from 4-5 psi to at least 20psi. The upgrade proved successful, and in 1846 the original 36”engine was replace by a new ‘Sims Combined’ Cornish engine also by Harveys. As part of the work, an extra boiler house was built and the original boiler house extended.

Cast-iron beam of the 1812 Boulton & Watt Engine at Crofton

The Great Western Railway took over the Canal in 1852 and further modifications were made over the following years, a new chimney in 1856, repairs to the 1812 engine after a major breakdown in 1896, new boilers in 1893 and 1903, a rebuilt boiler house roof in the early years of the 20th century and a major rebuild of the 1846 engine in 1905. Crofton kept steaming on through the first half of the 20th century as the canal declined; the end came in 1959 when the chimney became unsafe and was shortened by some 9m. This made it impossible to fire the boilers as there was not enough draught to make the boiler fires burn properly. But the station was not abandoned. There had been discussions about possible preservation, and Frank Wilmott, the station’s last engineman, was instructed to mothball the station rather than abandon it.

In 1962 the Kennet and Avon Canal Trust was formed with a view to reopening the canal. British Waterways, the then owners, had by this time installed electric pumps to feed the canal and had no further use for the pumping station and in 1968 the Trust purchased the site for 75 guineas. A group of enthusiasts including apprentices from Rolls Royce started the restoration work and in 1970 the late John Betjeman reopened the station and its working engines for the visiting public. Since the time Crofton and its engines has been lovingly maintained and operated by volunteers from all walks of life.

Pump Well and original section of Boulton & Watt engine pump rising main


C Ian Broom (2010) The Western Canal, Forerunner of the Kennet and Avon

Canal, The International Journal for the History of Engineering & Technology, 80:1, 1-21

C Ian Broom (2007) The History of Crofton Pumping Station on the

Kennet and Avon Canal, Transactions of the Newcomen Society, 77:2, 141-165,

C Ian Broom, The Crofton Story, Wiltshire Archaeological & Natural History Society, Devizes, 2013 ISBN 978 0 947723 16 3

Illustrations: All copyright Kennet and Avon Canal Trust