London's demonstrable ascendancy in the international trade of eighteenth-century England seems to have been sufficiently overwhelming to silence any twentieth-century doubts about its inevitability and the decline of its share in England's trade, from about three-quarters of its value at the beginning of the century to about two-thirds in the 1770s, can be dismissed as a comparatively minor statistical adjustment to a variety of healthy exogenous factors – such as the vigorous growth of transatlantic trade and the benign conjunctures which favoured the rising fortunes of Bristol, Liverpool and Glasgow. London, it seems agreed, was in possession of sufficiently strong institutional and resource endowments for its trading supremacy to survive the intermittent inconveniences of war, recession or changing fashions of demand.

Among those institutional endowments one must unquestionably include the port of London – but upon what basis? How clearly is the role of the port conceived by economic historians? How fully are its functions understood? Is it assumedto have operated impartiallyand cost-effectively for all the sectors it served – and, if not, what scale of diseconomies in London should be added to the normal tariff of transaction costs which all ports incur?