International actors represented a significant proportion of the collaborators and especially the correspondents of the British Board of Longitude - which encouraged navigation, technology and ‘science’ in general in addition to overseeing the large longitude rewards established by Parliament in 1714. These actors encompassed important collaborators such as the astronomers Tobias Mayer and Jérôme Lalande but also a host of correspondents who received varying degrees of encouragement.

The French were naturally best represented given the close, albeit often adversarial, relationship between the two nations and given the complementary work of Frenchmen including Lalande and of institutions including the Paris Observatory. However, correspondents also wrote from an array of other locations across Europe, Russia, and current and former colonies. The rewards and funding on offer, as well as the prestige of gaining the approval of the Board or of Commissioners such as Nevil Maskelyne and Joseph Banks, exerted a powerful lure on a wide variety of individuals.

Although a number of international wars were waged during the 114 years of the existence of the Board, international discord and competition seem to have had a limited effect beyond slowing communications. This was true despite actual attempts at international espionage, as when the French sent the clockmaker Ferdinand Berthoud to try to obtain the secrets of John Harrison’s timekeeper. However, the Board of Longitude and its associates seldom expressed concern about such threats, an exception being when the Commissioners briefly quizzed the chronometer maker Thomas Mudge about having discussed Harrison’s design with Berthoud in 1767.

By and large, the Board belonged to a network of international actors and correspondents who addressed the longitude and other issues in navigation, technology and ‘science’ in a surprisingly open manner. This openness was in part down to the importance these issues were often thought to have for ‘all mankind’, often in terms of trade, and to there being somewhat different approaches to viewing and communicating theories and data than there were to sharing concrete technologies such as chronometers. It was not until the late eighteenth and nineteenth centuries that the French, Spanish and other nationalities began to shift further away from close collaboration with the British in order to try to become more competitive in these areas of activity and manufacture.