The British were tentative about their settling at first, seeing formal colonisation as unnecessary and expensive, especially as their Empire was stretched. Then things changed comparatively quickly for a variety of reasons. Tensions grew between the recently arrived European settlers, and between Māori and Europeans.
In part in response to these escalating tensions, and in part due to a formalising of the colonisation intent, the Treaty of Waitangi was signed in 1840 between the British government and about 540 Māori tribal leaders. There are two versions of the Treaty - one in Te Reo Māori, Te Tiriti o Waitangi - and the other in English.