In October 2011 James Cracknell, two-time Olympic gold-medal rower and one of the greatest endurance athletes the world has ever known, suffered a seizure at home as his young son looked on in horror. A man who had known no limits, a man who had practically achieved the impossible, now struggled to master life's simple challenges. A year earlier, as James undertook yet another endurance challenge in Arizona, he was knocked off his bike by the wing mirror of a petrol tanker. It had smashed into the back of his head at high speed, causing severe frontal lobe damage. The doctors weren t sure if...