Across the main capitals of Europe, the traditional parties of the centre-left are in retreat. On Sunday, Germany’s Social Democratic party, the oldest and grandest of them all, went down to its worst postwar defeat at the hands of Angela Merkel’s centre-right Christian Democrats.

One day after the SPD scored just 23 per cent in the German poll, the ruling British Labour party saw its opinion poll rating in the UK fall to the same figure – in third place behind the Conservatives and Liberal Democrats.