Batman's Treaty with the Aborigines was annulled by the New South Wales governor (who at the time governed all of eastern mainland Australia), with compensation paid to members of the association. In 1836, Governor Bourke declared the city the administrative capital of the Port Phillip District of New South Wales, and commissioned the first plan for the city, the Hoddle Grid, in 1837. The settlement was named Batmania after Batman. However, later that year the settlement was named "Melbourne" after the British Prime Minister, William Lamb, 2nd Viscount Melbourne, whose seat was Melbourne Hall in the market town of Melbourne, Derbyshire. On 13 April 1837 the settlement's general post office officially opened with that name.