What is a fair voting system for the European Union? It looks as though, thanks to Poland, European leaders will be forced to debate this difficult question at their summit this week.

Since the simplified draft treaty is substantively identical to the old and rejected constitution - minus some cosmetics - the voting system proposed is going to be the same one: passage of legislation requires a coalition of countries representing at least 55 per cent of the member states and 65 per cent of the population. The Poles have threatened a veto unless the second of those two numbers is based on the square root of the population size - to reduce Germany's influence. It sounds arbitrary, but the Poles have a point. Mathematics is on the side of Poland.