In 1950, there were only two megacities, London and New York, with populations of more than 10m. In 2010, Tokyo was top of the list of the world’s largest cities, New York was only just scraping into the top 10, and London had dropped off the bottom. New York will join it in megacity oblivion in less than a decade and, with the exception of Tokyo, every other megacity will be in what is referred to as the 'global south'. To earn a place in the top 10, cities will soon need to boast a population of 20m or more. This is a new breed of city – the metacity."