Three months later, Shackleton regained the makeshift camp at Elephant Island, after two failed attempts.

ECONOMIST: Antarctic exploration

With no hope of being rescued from Elephant Island, Shackleton resolved to undertake the vastly improbable and daring voyage for which he would become justly famous.

ECONOMIST: Antarctic exploration

When eventually the floes began to break up in April 1916, Shackleton loaded his men into three small lifeboats and struck out for Elephant Island, an uninhabited speck of land some 100 miles distant.

ECONOMIST: Antarctic exploration

The peninsula is connected to the rest of the island by the Elephant Pass, a narrow causeway that the government has controlled for more than a decade from a huge military base.

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The peninsula is a haven for wildlife: humpback whales in the crystal blue water, elephant seals beached on Pleneau Island, squawking adelie, chinstrap and gentoo penguins, and wheeling cormorants, petrels and terns.

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Since then they have had a string of successes, gaining swathes of territory in the north, in April overrunning Elephant Pass, the disused but heavily defended land link between the peninsula and the rest of the island, and then very nearly recapturing Jaffna, which might have prompted a declaration of independence.

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