The High Commission of Australia in London is Australia's oldest diplomatic posting, having been established in 1910. Australia House became the site of the mission upon its opening in 1918. Prior to this, and prior to federation, Australia was represented through the Agents-General of the colonies, the oldest being New South Wales in 1864. The colonies became states upon federation in 1901 and many continue to be represented by Agents-General in London.
Four of Australia's Prime Ministers have later been appointed High Commissioner: Reid, Fisher, Cook and Bruce. Until 1973, every High Commissioner was a former member of the Australian Parliament and former minister. Since then, a number of senior career diplomats have held the post, although former politicians are still regularly appointed.