Bear Grylls knows what it takes to survive. But hes not the first. Take the American bombardier Louis Zamperini, who survived 47 days stranded at sea by catching and killing hungry sharks and drinking the warm blood of albatrosses - only to be captured by the Japanese and horrifically tortured for years in their most brutal POW camps.

Or Marcus Luttrell, a Navy SEAL who single-handedly took on a Taliban regiment before dragging his bleeding, bullet-ridden body for days through the harsh mountains of Afghanistan. Or Nando Parrado, one of the survivors of a horrific air-crash high in the ice-bound Andes, who only lived because he was willing to eat the flesh of his dead companions.

In this gripping new book, Bear tells the stories of the adventurers, explorers, soldiers and spies whose refusal to quit in the most extreme situations has inspired him throughout his life. Some of them make uncomfortable reading - survival is rarely pretty. But all of them are tales of eye-watering bravery, death-defying resilience and extraordinary mental toughness by men and women who have one thing in common: true grit.