Important political figures such as Konrad Adenauer, Winston Churchill, Harold Macmillan, François Mitterrand, Paul-Henri Spaak, Albert Coppé and Altiero Spinelli took an active role in the congress and a call was launched for a political, economic and monetary Union of Europe.
Fundo became acquainted with Altiero Spinelli and Sandro Pertini during this period, the latter urging Fundo to stay and fight with the Italian resistance.
During the Fascist regime, other prisoners were the future President of Italy Sandro Pertini, Umberto Terracini, Giorgio Amendola, Lelio Basso, Mauro Scoccimarro, Giuseppe Romita, Altiero Spinelli and Ernesto Rossi.
Among the other prisoners and friends of Eugenio Colorni on Ventotene were Ernesto Rossi and Altiero Spinelli, who in 1941 co-authored the famous Ventotene Manifesto "for a free and united Europe", i.e. an early sketch of a postwar democratic European Union.
The Ventotene Manifesto is a political statement written by Altiero Spinelli and by Ernesto Rossi while they were prisoners on the Italian island of Ventotene during World War II.