Accordingly, having made ready the James Caird, his largest lifeboat, for the voyage, at midday on 24th April, the very last day before the pack ice closed in again, Shackleton and five others – Worsley, Crean, McNeish, McCarthy and Vincent – set off through the Drake Passage – a name to bring dread even to seasoned mariners – in the almost impossible hope of making landfall on South Georgia, eight hundred miles away, and summoning help from the whaling stations there.

This journey involved a crossing of the world’s most inhospitable ocean in the depths of Antarctic winter. The boat was buffeted by mountainous and tempestuous seas. Ice built up on the decking, fifteen inches (750mm) deep, threatening to overturn the James Caird. Hour by hour, frostbitten and numbed with cold, they had to chip away from the vessel. At other times they were forced to bale for dear life. Their only solace was four hourly hot meals and the glimmer of a tiny primus stove. Their discomfort, hunched below in the James Caird’s cramped hold, must have been absolute.

But given Shackleton’s leadership, all six men’s sturdy seamenship and the amazing skills of New Zealander Frank Worsley, skipper of the Endurance, in charting a route for the James Caird by direct reckoning with only four sightings of the sun for Worsley to observe their position (April 26, May 3, 4 and 7 – the rest was dead reckoning) – they won through. After sixteen terrible days at sea, the James Caird sighted land at midday on Monday 8 May 1916.

All was by no means to prove easy, however, even now they had completed 800 miles. The boat arrived off South Georgia in hurricane conditions, and only at 5 p.m. on Wednesday 10th did they eventually manage to land, after tacking violently to make their way into a small, inaccessible inlet. Had they failed to make it, or had they overshot the island, Shackleton, his crew and the James Caird would have been either smashed to pieces and or swept beyond South Georgia, to be lost in mid-Atlantic.