With Maggie Black. Although holy men in India claim otherwise on their own behalf, every person on the planet has to divest themselves of wastes on a continuing basis. Yet 2.4 billion people still have nowhere decent or hygienic to do so. There are many reasons for the global sanitation crisis, from technological to economic to political. But overshadowing them all are the socio-cultural taboos surrounding these unfortunate bodily processes and what to do with their result. Maggie Black has been writing on water, sanitation and hygiene issues as they affect people in poor communities in Africa, Asia and Latin America since she was first commissioned by UNICEF to write a book for the 1990s Water and Sanitation Decade. Several others followed, culminating in The Last Taboo published for World Sanitation Year 2008. She now revisits the topic and asks: Has anything changed?

Nearest tube station Farringdon. 6.45pm (doors open 6.30).