In 1904, Sir Francis Bertie, the British ambassador at Rome, complained about his lack of influence. Recalling fondly his days at the Foreign Office, Bertie lamented: ‘In Downing Street one can at least pull the wires whereas an Ambassador is only a d…d marionette’. Bertie's view is generally accepted by historians, who argue that the role of diplomats declined in the late nineteenth and early twentieth centuries. At one level, there is little doubt that such a view is correct; after the invention of the telegraph, British diplomats did not make policy in the fashion supposedly done by Stratford Canning at Constantinople before the Crimean War.

To note that ambassadors did not make policy is one thing; to then assert that they counted no more than as marionettes is another. To do so is both to oversimplify the role of ambassadors and to underestimate the influence that they were able to exert on policy by other than direct means. British ambassadors affected British foreign policy in a number of ways. First, ambassadors and their staffs provided the Foreign Office with the bulk of information about the countries to which they were accredited. This was important, both in the wider sense that ambassadors were responsible for keeping the Foreign Office well informed about such matters as their host country's economic and military strength, and in the narrower sense that the ambassadors were expected to provide their superiors in Whitehall with an accurate assessment of the personalities and political influence of those in positions of power. By doing so, ambassadors helped to create the ‘mental map’ that served to determine British policy. Second, ambassadors were the embodiment of Britain abroad.