During the Napoleonic Wars ‘horse-power’ became expensive due to the lack of domestic horses so George Stephenson, an engineer from Newcastle, experimented with steam power as alternative transport. By feeding coal into boilers steam could be produced, allowing heat energy to be converted into mechanical energy, so that steam engines could be mobile. By 1830 this technology had developed into the first passenger railway services. In 1827 George Hudson, a draper in what is now the National Trust Shop, inherited £30,000 and took a huge risk by investing in the North Midland Railway. By 1837 he was Lord Mayor of York and ‘Railway King’, controlling over 1,000 miles of track. Within ten years he was bankrupt and in disgrace was imprisoned from 1865 to 1866. The effect of the advancement of the railways to York’s prosperity is today reflected by the presence of the National Railway Museum.