During the reign of Queen Victoria, Glasgow became the 'second city' and workshop of the British Empire. Over the same period, Clydeside's adopted son, William Thomson (1824-1907), rose from College student to first Lord of British science, Baron Kelvin of Largs and, ultimately, was given a resting place alongside Sir Isaac Newton in Westminster Abbey. In this paper, the author places Kelvin in the context of his city and Empire, showing how both his life and his science expressed his active participation in 19th century industrial society. Very soon after his appointment to the Glasgow University chair of natural philosophy (physics) at the remarkable age of 22, William Thomson embarked on a series of investigations which led him to construct a new kind of physics, the science of energy. Reacting against the action-at-a-distance force physics of the French savants, notably Laplace and Poisson, Thomson employed the engineering concept of 'work' to set forth the principles of thermodynamics, to formulate a new 'field' approach to physical phenomena, and to present a radically-reformed system of cosmology. Introducing the term 'energy' into the scientific language, he skilfully promoted the new science of energy through the British Association for the Advancement of Science such that by the late 1860s Thomson's approach had become thoroughly established as the quintessential British style of mathematical physics in the second half of the 19th century.