Opulent eastern cities were still reeling from Alexander's devastating conquests when Pytheas the Greek adventurer quietly slipped moorings at Massalia in southern Gaul to face the unknown ocean and explore the remote north. Pytheas the adventurer, who rounded Britain and even ventured as far as the Baltic Sea so long ago, is a fascinating enigma. What inspired him to do it? Adventure? Trade? The pursuit of knowledge? Or had he personal reasons? Not only an educated adventurer who survived to write two books, Pytheas was surely young to embark on such a gruelling and hazardous expedition.He was also clearly familiar with celestial navigation and ships - as would any merchant who traded out of Massalia. Only fragments and reference to his accounts remain, yet such were his revelations that 200 years on the Roman geographer Strabo, who never went beyond the straits of Sicily, called him a lying fantasist...because Pytheas also claimed to have ventured far beyond Britain to a mysterious place called Thoule. Not only were his astronomical observations there used by ancient scholars to prove that the earth was a sphere, tantalising hints reveal what else Pytheas recorded of that extraordinary three year expedition. But what of Pytheas the man? Who went with him? How did they travel such distances - and get by hostile Phoenicians who controlled access to the great ocean?