Sir Ernest Shackleton, the great Polar explorer whose famous Endurance expedition sailed into the ice exactly 100 years ago this month, is a writer’s dream. He was a charismatic man of enormous courage whose exploits in the Antarctic defy belief and yet he was also a complex character full of paradoxes.

My book is the first comprehensive account of his life to be written in 30 years, and what drew me to the story is that there were, in effect, two Shackletons. On the ice, he was a heroic, pioneering and inspirational explorer whose incredible adventures paved the way to the South Pole for Amundsen and Scott. However, on dry land, Shackleton was a restless, unfulfilled character who struggled with domesticity and the challenges of holding down a job and leading a normal married life.

As an explorer, Shackleton ranks alongside the great voyagers like Columbus, Captain Cook and Lewis & Clark. He opened up the Antarctic on four expeditions to the continent in the space of 20 years and it was Amundsen, the finest of all Polar explorers, who once said, “Sir Ernest Shackleton’s name will for evermore be engraved with letters of fire in the history of Antarctic exploration.”

However, at home he was a failure, his chaotic private life involving string of affairs and a series of failed business ventures. He left behind a trail of debts and nurtured a child-like longing to search for buried treasure, as though a unearthing a pot of gold would solve all his money worries. El Dorado, though, always remained beyond his grasp.

Shackleton first went to the ice in 1901, forcing his way onto Scott’s Discovery expedition because he became friendly with the enterprise’s principal sponsor. In 1907, he led his own expedition to Antarctica on what became his greatest feat of exploration. Despite unbearable hardships and poor provisioning, Shackleton’s party of four men discovered the route to the South Pole later followed by Amundsen and Scott.

Shackleton led his weak and starving men to within 97 miles (geographic) of the Pole and was brave enough to turn back within sight of his goal because he did not have enough food to get back to base camp. A few extra pounds of provisions would have carried him to the South Pole but Shackleton put the lives of his men first and blithely told his wife, “I thought you would prefer a live donkey to a dead lion.”

His greatest adventure, which began in December 1914, saw Shackleton’s expedition ship Endurance crushed by the ice and the 28-man party cling to life on an ice floe for 16 months. Shackleton left 22 men on the bleak Elephant Island and sailed the small open boat James Caird to South Georgia to fetch rescue. Not a man was lost.

Shackleton’s genius for leadership was the crucial difference in the struggle for survival. He never took unnecessary risks or asked his men to do anything he would not do himself. His unwavering optimism inspired his men to believe they would survive and chimed with Napoleon’s remark, “A leader is a dealer in hope.” Today American business schools teach Shackleton’s leadership style to budding entrepreneurs.

As though choreographed, Shackleton died in January 1922 at South Georgia on the edge of the Antarctic wilderness. He was preparing for another voyage into the ice where his restless soul at least found peace.

Shackleton loved poetry and there was a poetic postscript to his life. Upon being told that her husband had died in South Georgia, his wife cabled his comrades with the simple instruction: “Bury him where he was happiest.”

He lies to this day in South Georgia overlooked by towering mountains and glaciers.