We've always built memorials to our dead. But how do our memorials and commemorations differ across cultures and how are they changing in the 21st Century? Why do we have different types of memorials for different kinds of death? In the third part of our Dead Calm series, Hilary Harper, Lyndon Ormond-Parker, Joy Damousi and Bjorn Nansen explore the role, relevance and relief offered by memorials after death and disaster. What do official and unofficial commemorations mean and how do they affect the ways we mourn?