The United Kingdom formally annexes the Tristan da Cunha archipelago, administering the islands from the Cape Colony in South Africa.

The Cape Colony (Dutch: Kaapkolonie), also known as the Cape of Good Hope, was a British colony in present-day South Africa named after the Cape of Good Hope, which existed from 1795 to 1802, and again from 1806 to 1910, when it united with three other colonies to form the Union of South Africa.

The British colony was preceded by an earlier corporate colony that became an original Dutch colony of the same name, which was established in 1652 by the Dutch East India Company (VOC). The Cape was under VOC rule from 1652 to 1795 and under rule of the Napoleonic Batavia Republic from 1803 to 1806. The VOC lost the colony to Great Britain following the 1795 Battle of Muizenberg, but it was acceded to the Batavia Republic following the 1802 Treaty of Amiens. It was re-occupied by the British following the Battle of Blaauwberg in 1806, and British possession affirmed with the Anglo-Dutch Treaty of 1814. The Cape of Good Hope then remained in the British Empire, becoming self-governing in 1872.

The colony was coextensive with the later Cape Province, stretching from the Atlantic coast inland and eastward along the southern coast, constituting about half of modern South Africa: the final eastern boundary, after several wars against the Xhosa, stood at the Fish River. In the north, the Orange River, natively known as the Narib (Black River) and subsequently called the Gariep River, served as the boundary for some time, although some land between the river and the southern boundary of Botswana was later added to it. From 1878, the colony also included the enclave of Walvis Bay and the Penguin Islands, both in what is now Namibia.

It united with three other colonies to form the Union of South Africa in 1910. It then was renamed the Province of the Cape of Good Hope. South Africa became a sovereign state in 1931 by the Statute of Westminster. In 1961, it became the Republic of South Africa. Following the 1994 creation of the present-day South African provinces, the Cape Province was partitioned into the Eastern Cape, Northern Cape, and Western Cape, with smaller parts in North West province.

Tristan da Cunha (), colloquially Tristan, is a remote group of volcanic islands in the south Atlantic Ocean. It is the most remote inhabited archipelago in the world, lying approximately 1,732 miles (2,787 km) off the coast of Cape Town in South Africa, 1,514 miles (2,437 km) from Saint Helena and 2,487 miles (4,002 km) off the coast of the Falkland Islands.The territory consists of the inhabited island, Tristan da Cunha, which has a diameter of roughly 11 kilometres (6.8 mi) and an area of 98 square kilometres (38 sq mi); the wildlife reserves of Gough Island and Inaccessible Island; and the smaller, uninhabited Nightingale Islands. As of October 2018, the main island has 250 permanent inhabitants, who all carry British Overseas Territories citizenship. The other islands are uninhabited, except for the South African personnel of a weather station on Gough Island.

Tristan da Cunha is a British Overseas Territory with its own constitution. There is no airstrip on the main island; the only way of travelling in and out of Tristan is by boat, a six-day trip from South Africa.