This article examines issues of island sovereignty and lighthouse administration in maritime Southeast Asia in the context of post-war decolonisation. It does so by demonstrating how lax and complacent colonial governance in British North Borneo led to the construction of a lighthouse on contested island territory. By the late 1940s these islands became the focal point of a regional dispute between the Philippines, North Borneo's colonial government, and the United Kingdom. While lighthouses were, in the colonial mind-set, deemed essential for illuminating the coasts and projecting order onto the seas, the Philippine government sought to renege on colonial-era obligations and wrest a new sense of post-colonial legitimacy.

The legacy of the Turtle Island transfer was therefore significant in recalibrating imperial lighting in the Sulu Sea, as well as giving rise to a Philippine post-colonial authority that was characterised by an acknowledgement of indigenous Suluk maritime heritage. Similarly, it reflected an extension of previous instances of transnational disputes in the region, where the island shoal had been simultaneously claimed and administered by the United States, the United Kingdom and the historical Sulu Sultanate. While the lighthouse remained destroyed, and the seas dimmed, by mid-1948 the Turtle Islands had attained a new post-colonial and transnational status. Utilising a range of archival sources, memoirs and published material, this article sheds light on an under-examined period of Southeast Asian history.