William Mackinnon's business career spanned most of the second half of the nineteenth century. It extended from the repeal of the Corn Laws and the Navigation Acts, which finally converted Britain and its overseas possessions into one large free-trade zone, open to international trade and investment, to the advent of the ‘New Imperialism’, when apprehension arose about British industrial and military/naval power being surpassed by Germany and the USA and the first doubts began to appear about the continuing usefulness of free-trade policies. The second half of the century was also a period when, despite the disappearance of earlier mercantilist justifications for overseas expansion, the British Empire continued to expand. Substantial emigration to the ‘colonies of settlement’, in North America, Australasia and southern Africa, further military conquests within the Indian sub-continent and along the margins of its ‘sphere of influence’, and participation in the competitive ‘scramble’ for new tropical territory in Africa, south-east Asia and the Pacific, meant that the Victorian Empire grew to incorporate about a quarter of the world's population by the time of the ‘celebration of empire’ that was the Diamond Jubilee of 1897. It was a period, too, in which Britain's mercantile marine was dominant in world trade and a major source of the ‘invisible earnings’ that enabled Britain to pay its way within the international economy. The total tonnage of vessels registered in Britain rose from 3,565,133 tons in 1850 (95.3 per cent of it sailing ships) to 9,304,108 tons in 1900 (77.5 per cent of it steam ships). Two factors in particular underlay the growth of the mercantile marine. The first was the general thrust of the ‘open economy’ model of behaviour, which emphasised the comparative advantages of trade, encouraged the exchange of British manufactures and services for raw materials, foodstuffs and certain specialised ‘finished’ goods, and created additional demands for transportation of goods and people. The second was the technological lead which the pioneering development of the iron- and steel-hulled steamship, together with successive innovations in marine engines, propulsion systems, hull-design and on-board and dockside cargo-handling machinery, gave to British shipowners and managers.