The sharing of some services and facilities abroad by Canada and Britain – as opposed to the shaping and expression of foreign policy – is an entirely reasonable measure, spreading costs for both nations.
Indeed, Canada has had an agreement for consular services with Australia since 1986, when Joe Clark was the minister of external affairs. On Monday, John Baird, the Minister of Foreign Affairs, in his appearance with the British Foreign Secretary, William Hague, offered one humdrum example of such co-operation: giving a British official a spare office in the Canadian embassy in Port-au-Prince, Haiti.
Foreign policy is another matter. The core functions of ambassadors have been modified since modern diplomacy – or something like it – took shape in the 15th and 16th centuries, but there has also been a high degree of continuity. For example, many of the diplomatic documents obtained by hacking and released by WikiLeaks were of much the same character as the letters sent by ambassadors to their masters at home, 500 years ago.
Previously, "embassies" had been specific visits with specific purposes. Resident envoys evolved, first in Italy, then in all of Western Europe, partly because of the decline of overall papal authority and the failure of the Holy Roman Empire to be a real empire, as is recounted in an excellent book by the late American historian Garrett Mattingly, Renaissance Diplomacy. Such a diplomatic system expressed a balance of power, rather than the the supremacy of a single great power.
The speed and versatility of modern communications make an enormous difference to international relations, but they do not simply displace the real and enduring value of physical presence and face-to-face communications. Conceivably, some three-dimensional version of Skype could eventually do what ambassadors do and what visits of heads of government achieve. But not yet.
For the less contentious and less political matters, everything from emergency preparedness and response to to the routine processing of visas, co-operation among countries with similar cultures and shared history makes sense. To share certain costs is not to revert to membership in the British Empire.