For two parties that have been enemies for so long -- indeed, whose hostility basically created the modern two-party system -- Britain's Conservatives and Liberal Democrats haven't done too badly at working together in a coalition government.

This week, however, that government has come under stress with two disputes over electoral reform. Yesterday, Conservative Prime Minister David Cameron announced that he would press ahead with proposed reform of electoral boundaries, despite the opposition of Deputy Prime Minister and Lib Dem leader Nick Clegg.