In this presentation, we examine the roles played by gatekeepers, assistants, informants, and amateur ethnographers in the Cambridge Anthropological Expedition to the Torres Straits (1898-99), a benchmark in the history of British anthropology. To do this, we have analyzed various documents, including the diary Haddon kept during the expedition and his extensive correspondence with various people in the field, which is housed in the Cambridge University archives. Without the participation of this network of collaborators, the expedition would not have achieved its aims. Many islanders collaborated with the expedition members, providing them access to the field, contacts, information, means of communication, and material resources. In many cases, they held traditional positions of leadership within their communities, and colonial authorities had formalized their status as representatives of law and order by giving them the title of "mamoose" (chief). Two of them, Waria and Pasi, made significant ethnographic contributions to the expedition. Additionally, Haddon utilized his contacts with missionaries, colonial officers, and traders established during the expedition he had conducted a decade earlier to plan and conduct the ethnographic research. Furthermore, in the field, Haddon encountered someone who could well be considered an eight member of the expedition, Jack Bruce, the schoolteacher of Mer. Both maintained an extensive exchange of data and ideas in the field and later through extensive correspondence, which was subsequently reflected in the fifth volume of the expedition Reports. This network of contacts shows how, from its origins, ethnographic work was a collaborative endeavor, the result of teamwork among various actors in the field, and not a solitary and individual task as 20th-century anthropology came to represent.