Despite Cook's "discoverer's" claim in 1769, imperial cartographers had never marked New Zealand as a British possession and it was with some reluctance - informed by the perception of an over-extended empire only marginally under control - that New South Wales law was nominally extended to New Zealand in 1817. The effect was minimal; the New South Wales governor had no official representation on this side of the Tasman and was powerless to act. Unimpressed, by 1831 a small group of northern Maori chiefs decided to petition the British monarch to become a "friend and the guardian of these islands", a letter that was later used to justify Britain's intervention.

Britain's response was to send the pompous and less-than-competent James Busby as British Resident in 1833, with a brief to encourage trade, stay on good terms with the missionaries and Maori, and apprehend escaped convicts for return to Sydney. Feeling that New Zealand was becoming a drain on the colony's economy, the New South Wales governor, Bourke, withheld guns and troops, and Busby was unable to enforce his will. Busby was also duped by the madness of Baron de Thierry, a Brit of French parents, who claimed he had bought most of the Hokianga district from Hongi Hika and styled himself the "sovereign chief of New Zealand", ostensibly to save Maori from the degradation he foresaw under British dominion. In a panic, Busby misguidedly persuaded 35 northern chiefs to proclaim themselves as the " United Tribes of New Zealand " in 1835. As far as the Foreign Office was concerned, this allowed Britain to disclaim responsibility for the actions of its subjects.

By the late 1830s there were around two thousand pakeha in New Zealand, the largest concentration around Kororareka in the Bay of Islands, where there were often up to thirty ships at anchor. Most were British, but French Catholics were consolidating their tentative toehold, and in 1839 James Clendon was appointed American consul. Meanwhile, land speculators and colonists were taking an interest for the first time. The Australian emancipationist, William Charles Wentworth, had "bought" the South Island and Stewart Island for a few hundred pounds (the largest private land deal in history, subsequently quashed by government order) and British settlers were already setting sail. The British admiralty finally began to take notice when it became apparent that the Australian convict settlements, originally intended simply as an out-of-sight, out-of-mind solution to their bulging prisons, looked set to become a ­valuable possession.

It was a combination of these pressures and Busby's continual exaggeration of the Maori inability to control their own affairs that goaded the British government into action. The result was the 1840 Treaty of Waitangi , a document that purported to guarantee continued Maori control of their lands, rights and possessions in return for their loss of sovereignty, a concept poorly understood by Maori. The annexed lands became a dependency of New South Wales until New Zealand was declared a separate colony a year later.