When you see your nation's flag fluttering in the breeze, what do you feel?For thousands of years flags have represented our hopes and dreams. We wave them. Burn them. March under their colours. And still, in the 21st century, we die for them. Flags fly at the UN, on the Arab street, from front porches in Texas. They represent the politics of high power as well as those of the mob. From the renewed sense of nationalism in China, to troubled identities in Europe and the USA, to the terrifying rise of Islamic State, the world is a confusing place right now and we need to understand the histories, the power and the politics of the symbols that people are rallying round; the symbols that unite us - and divide us.