Late afternoon at John Rennie the Elder's Claverton Pumping Station near Bath on a beautiful April day. This fascinating feat of engineering deserves to be much better known than it is, for it is unique – there is nothing else like it anywhere in the world as far as can be ascertained. Built in the very early 1800s, it used the power of the fast-flowing River Avon to raise water forty-eight feet up to the Kennet and Avon Canal. When he was building the canal, Rennie understood that there was a great need to pump water up to its highest points as there were no feeder streams which could be diverted to keep the upper locks full. At Crofton as few miles west near Hungerford, he had built a steam pumping station using two large beam engines to raise water, but at Claverton he evolved this hybrid solution to the problem – employing the tried-and-tested ancient technology of a breast-shot watermill to drive the beam engine pumps. A very 'green' solution – no fuel costs, no pollution!