Thomas Edison once said, “I have not failed. I’ve just found 10,000 ways that won’t work.” Innovation is a process of failure and learning from failure. The same is true in development cooperation. Take PlayPumps for example, which aimed to take the energy produced by children playing on a merry-go-round to pump water up from a borehole, supplying villages with clean, effortless drinking water. An inspired, ingenious plan – how could, and did, it go wrong?