The NHS were facing a serious problem: although sign-ups for blood donors were on track, not nearly enough people were actually attending the centres. And, of those that were, we lacked the ethnic diversity necessary for addressing conditions like sickle cell. Carat needed users to take action at a community level. We needed people to know that they, personally, could be part of the solution. But first we had to find these specific, altruistic people. Simply put, we built a predictive model and a campaign we can turn on/off when appointments are available, this delivered outstanding results.