It all began in a railway carriage. Two businessmen, travelling to the Kingston Assizes in Surrey, nodded to each other as strangers do, but did not strike up a conversation. They were expert witnesses appearing for different sides in the Croydon Water Question; a legal test case that boiled down to who owned the undergroundwaters of London (Mather 2008: 83–4). Joseph Prestwich (Figure 1a), the older by 11 years, represented the water suppliers. As the train rattled along under full steam he would have seen landmarks from his pioneering geology of the London Basin. But water was not his business. His family ran a profitable wine importers. Geology, however, was his passion.