I’ve always been interested in trying new things,’ Tim Jarvis declares disarmingly in the opening  line of The Unforgiving Minute, ‘and I’m not sure I know exactly why.’ Unlike Scott or Shackleton, Jarvis has no literary aspirations but is a knockabout bloke who gives motivational talks on his adventures and who believes in a gospel of personal effort, physical challenge and – trailing these two by a long margin – the wonder of the natural world. This account of a series of polar journeys is self-consciously structured using the effective journalistic device of plunging the reader into an intense situation at the opening of each chapter, and finishing each chapter with a teaser for the next. Like most accounts of polar exploration, it is a weird blend of numbing dullness and compulsive interest. Jarvis has taken the lessons of his public speaking and turned them into a pleasing book, firmly in the self-help genre, with gripping accounts of the many crises that inevitably beset extreme adventure expeditions, not to mention the prurient details of toilet habits, tooth decay and muscle wastage.