In 1835 a company of Tasmanian adventurers claimed to have made a treaty to purchase 500,000 acres of the Aboriginal people’s land in an area of Port Phillip Bay, which later became the city of Melbourne. It is the only such treaty known to have been struck in the Australian colonies, and it was quickly repudiated by the imperial and colonial governments. Why did those colonial land grabbers try to purchase the Kulin people’s land at Port Phillip when other adventurers and government officials had merely taken possession of the land as though it had no owners? Why did they represent the deed of purchase they drew up as a treaty? How did the Kulin people understand the treaty? Why did the imperial and colonial governments reject their treaty-making? More generally, why did imperial and colonial authorities in the Australian colonies refuse to recognise the Aboriginal people’s sovereignty and rights in land, which contrasted markedly to their approach to these critically important matters in other British settler colonies