One hundred years ago this week, in late August 1915, 28 British and Irish explorers loitered helplessly, hungry and cold, as they awaited the sinking of the ship that had taken them 10,000 miles to the frozen wastes of Antarctica. The ice-trapped Endurance was being slowly crushed to splinters.
The sun had disappeared below the horizon in May, cloaking the men in 24-hour darkness for three months.
It would be three months more before the Endurance finally slipped into its watery grave. The return of daylight had eased conditions but a mute despondency settled upon the men, as their own demise crept nearer. But one man moved quickly to inject spirit and hope into those who'd followed him to the ends of the Earth.
Cold, remote and lifeless, the Antarctic was the final frontier of its time. Its conquest was the space programme of its day. By 1915 Kildare-born Ernest Shackleton had become one of the Big Three of so-called Heroic Age Of Antarctic Exploration, while one of the other two, Robert Scott, had perished returning from the Pole. With the Pole ticked off the 'to-do' list, Shackleton intended being first to cross the continent coast-to-coast.
Faced with what looked like 28 certain deaths, Shackleton manned up magnificently.
As soon as the Endurance became trapped, the Irishman introduced a things-to-make-and-do schedule aimed at keeping up morale and putting in place an escape plan.
He ordered that the ship's three lifeboats be brought onto the pack ice and built up with extra timbers to face the planet's cruelest seas.
Aware that they'd have to dig in for the long, sunless winter, he had the Endurance stripped and cannibalised to construct the warmest possible shelters.
An veteran of icy adventures, Shackleton had honed a gift for man-management. According to the author of Shackleton's Boat, just published by Collins Press: "As large floes drifted apart and then crashed together again their violence was tremendous. It was extremely unnerving and the uncertainties could have devastated morale. It was then that Shackleton came into his element.
He seemed to thrive in these conditions, always devising competitions and entertainments such as sing-songs to keep everyone occupied.
Tireless and full of resource, he imbued his men with his sense of self-confidence until they came to believe that they could overcome any crisis.
Nevertheless, the supreme test was yet to come. In fact, there were to be two supreme tests. The group were stuck on an ice floe drifting northwards towards warmer climes. Eventually it would melt from under them, although there was a good chance that they'd have died from starvation before that happened.
Shackleton ordered a forced march, dragging their reinforced lifeboats. With the return of daylight they found themselves sinking up to their waists in slush, so they trekked by night when a crust of surface ice formed.
The ice did indeed melt from under them and the 28 men rowed to an isolated barren rock called Elephant Island. Knowing that they would soon starve to death, Shackleton and five others set out to seek help, leaving 22 behind.
While Shackleton's courage and sense of duty were beyond reproach, he was also deeply motivated by the need to preserve his legacy. As they set off on their perilous mission he told his lieutenant Frank Worsley of his fear that: "If things went wrong, it might be said that I abandoned them."
Miraculously, after 800 miles in an open-top boat on merciless seas, they reached a whaling station and effected the rescue of all 22 castaways.
Already knighted for an earlier mission, Shackleton returned to a hero's welcome, with the Irish and British newspapers fighting to claim him as one of their own.
After the great wave of adulation that greeted him, Shackleton once again proved that he was more at home off adventuring than coping with the hum-drum realities of 'civilisation'.
Business ventures in tobacco, mining and postage stamps flopped and he died penniless in 1922 from a heart attack on expedition.
As the sun set on Empire in the 1960s, a nostalgia for his heroic gumption took root and his reputation has grown, as can be gauged from the sale of a tin containing his biscuit crumbs for €10,000 at auction in 2001.
'Shackleton's Boat' by Harding McGregor Dunnett is published by Collins Press