It is one of the most remote islands in the world, and was uninhabited when discovered by the Portuguese in 1502. It was an important stopover for ships sailing to Europe from Asia and South Africa for centuries. Napoleon was imprisoned there in exile by the British, as were Dinuzulu kaCetshwayo (for leading a Zulu army against British rule) and more than 5,000 Boers taken prisoner during the Second Boer War, including Piet Cronjé.
Between 1791 and 1833, Saint Helena became the site of a series of experiments in conservation, reforestation and attempts to boost rainfall artificially. This environmental intervention was closely linked to the conceptualisation of the processes of environmental change and helped establish the roots of environmentalism.
Saint Helena is Britain's second-oldest overseas territory after Bermuda.
Most historical accounts state that the island was sighted on 21 May 1502 by Galician navigator João da Nova sailing in the service of Portugal, and that he named it Santa Helena after Helena of Constantinople. Another theory holds that the island found by da Nova was actually Tristan da Cunha, 2,430 kilometres (1,510 mi) to the south, and that Saint Helena was discovered by some of the ships attached to the squadron of the Estêvão da Gama expedition on 30 July 1503 (as reported in the account of clerk Thomé Lopes). However, a paper published in 2015 reviewed the discovery date and dismissed 18 August as too late for da Nova to make the discovery and then return to Lisbon by 11 September, whether he sailed from Saint Helena or Tristan da Cunha.
It demonstrates that 21 May is probably a Protestant rather than a Catholic or Orthodox feast day, and the date was first quoted in 1596 by Jan Huyghen van Linschoten, who was probably mistaken because the island was discovered several decades before the Reformation and the start of Protestantism. The alternative discovery date of 3 May is suggested as being historically more credible; it is the Catholic feast day of the finding of the True Cross by Saint Helena in Jerusalem, and cited by Odoardo Duarte Lopes and Sir Thomas Herbert.