Jack London was born in San Francisco in 1876. He is best known for his novels "The Call of the Wild" and "White Fang," written either side of his writing "The Sea Wolf." Coming from a working class background and having served a prison sentence for vagrancy in his youth, London would go on to become an activist for social reform. He died in 1916, aged just 40.Bear Grylls went from Eton to the SAS before a near-fatal spinal injury ended his career in the military elite. His undeterred thirst for adventure led him to become the star of the TV show "Born Survivor," which has been seen by over a billion viewers worldwide.