Val Curtis of the London School of Hygiene and Tropical Medicine explains how we can save millions of live by washing our hands after going to the toilet, and especially before eating food. She was talking at a party for primary school children held in London's Science Museum to celebrate Global Handwashing Day, where Grace Mukasa chief executive of AMREF (African Medical And Research Foundation) and perfume expert Kate Williams from the Seven Scent company add their comments on how best to help children learn the habit of washing their hands.