Virtually everyone associates Costa v ENEL with the establishment of the principle of supremacy of European law, yet the story of that lawsuit is still known but to a few. What drove Flaminio Costa to sue his electricity provider over a bill of as little as £1925 (about €22 in 2018)? Why did the small-claims court of Milan decide to involve both the Italian Constitutional Court and the European Court of Justice in such a ‘minor’ lawsuit? Why did those two courts hand down judgments going in opposite directions? How did the lawsuit end when it came back to Milan small-claims court? Relying upon previously undisclosed court documents and interviews with some of the actors involved, this paper seeks to shed some light on the less-known aspects of the Costa v ENEL lawsuit, against the background of electricity nationalization in Italy at the height of the Cold War, and to assess the contribution of the ‘architect’ of that lawsuit, Gian Galeazzo Stendardi, to the development of the doctrine of supremacy of European law.