When our friends at the Irish Blood Transfusion Service asked us to create an ad campaign to start a movement, we suggested trying it the other way round. So we went to Skerries, asked seven existing donors to recruit new donors, and turned the movement they initiated into a campaign of seven web films. The data point we used to incite behaviour change was simple: 1 in 4 people will need a donation in their lifetime. But only 3% of people donate. Already, change is happening.