Another ‘oldest’ question that’s not as simple as it might seem.
Austria has occupied a building at 18 Belgrave Square in Belgravia since it moved there from Chandos House in Queen Anne Street in 1866.
But the embassy was vacated with the outbreak of World War I and the building entrusted, firstly to the protection of the ambassador of the United States, and following the severing of their relations in 1917, to the Royal Swedish Legation.
The Austrians returned in 1920 but following Hitler’s incorporation of Austria into the German Reich in 1938, it was used as a department of the German Embassy.
Following the outbreak of World War II, the Swiss legation room over protection of the building and following the end of the war the damaged building fell under the care of Britain’s Ministry of Works.
The Austrians returned in September, 1948, with the new ambassador arriving in 1952. It continues today to serve as the residence of the Austrian Ambassador.
Not to be confused with the Austrians, the Australian High Commission resides in ‘Australia House’ which claims to be “the longest continuously occupied foreign mission in London”.
In 1912, the Australian Government bought the freehold of a site on the corner bounded by Strand, Aldwych and Melbourne Place. Following a design competition, Scottish architects A Marshal Mackenzie and Son were selected as the designers of the new Australia House with Commonwealth of Australia’s chief architect, Mr JS Murdoch, arriving in London to assist them.
Work began in 1913 – King George V laid the foundation stone – but was interrupted by World War I and in 1916, former Australian PM and now High Commissioner Andrew Fisher moved into temporary offices on the site even as the work continued around him. King George V officially opened Australia House on 3rd August, 1918, with then Australian Prime Minister, WM “Billy” Hughes, in attendance.