AP Photo

This is an important week for the politics and policy of Britain, but not for any reason connected to the froth of party conferences, prescription drugs or Sun editorials. The reasons lie across the sea in Ireland and across the channel in Germany, in the choices being made by voters there. Those votes can — and should — alter the choices and opportunities faced by Britain and, crucially, by its likely Conservative government.

Tomorrow a couple of million Irish voters will seal the fate of the Lisbon treaty, the document that hardly anyone has read and which will determine the powers and institutional structure of the European Union for at least the next decade. Having rejected the treaty in a referendum last year, the Irish are being sent back to the polls in order...