How many British expeditions to the Antarctic were led by Ernest Henry Shackleton?

Ernest Henry Shackleton (15 February 1874 – 5 January 1922) was a British Antarctic explorer who led three British expeditions to the Antarctic. He was one of the principal figures of the period known as the Heroic Age of Antarctic Exploration.

Born in Ireland, Shackleton and his Anglo-Irish family moved to Sydenham in suburban south London when he was ten. His first experience of the polar regions was as third officer on Captain Robert Falcon Scott's Discovery expedition of 1901–1904, from which he was sent home early on health grounds after he and his companions set a new southern record by marching to latitude 82°S. During the Nimrod expedition of 1907–1909, he and three companions established a new record Farthest South latitude at 88°S, only 97 geographical miles (112 statute miles or 180 kilometres) from the South Pole, the largest advance to the pole in exploration history. Also, members of his team climbed Mount Erebus, the most active Antarctic volcano. For these achievements, Shackleton was knighted by King Edward VII on his return home.