By Mitch Phillips RIO DE JANEIRO, Aug 18 (Reuters) - The Brownlee brothers' incredible demolition of the best of the rest of the world in Thursday's Olympic triathlon might have looked straightforward but to deliver a textbook race in Rio they had to go through "hell" first. Alistair, 28, became the first triathlete to retain an Olympic title and Jonny, 26, added a silver to the bronze he picked up in London four years ago. Alistair took time to savour the moment, walking down the finish chute holding the Union Flag aloft, before collapsing and embracing his brother, who had suffered similarly in the searing Rio heat. More...