Robert Peary's diary entry for April 23 1909 was full of the elation of a man who claimed - controversially - to have become the first western explorer to reach the North Pole. His life's work had "ended accomplished", he reflected, after more than two decades of "effort, hard work, disappointments, hardships, privations, more or less suffering & some risks".

"I have got the North Pole out of my system," he wrote. "I have won the last, great geographical prize . . . for the credit of the US, the Service to which I belong, myself, & my family."