Received wisdom is that the German fiscal position is unassailable. It's true the annual budget deficit there is just 4.3pc of GDP but total debt will rise to 83.2pc of GDP this year, not far off Portugal at 93.3pc and already ahead of France (82.3pc) and Spain (61pc). The German economy, and its management, is seen as being too strong to allow its debt position to get out of hand. But on Tuesday the Bundesbank reminded us that such assumptions are prey to unforeseen events - notably the central bank's decision to downgrade its forecast for German growth next year to just 0.5pc.