The biggest question about China at the moment is the buoyancy of its economy. Suddenly there are serious worries.

In China people might believe Americans wish for their economic collapse. This is not true. If only because of the intimate interdependence and indeed inter-reliance of our two great economies, those days of evil thinking are long gone.

Imagine this of China today: that its economy, directed by a Beijing control tower, holds 1.35 billion people in a giant jetliner that once required an eternity to take off but, once airborne (as it has been, remarkably, for two decades), must maintain a minimum speed to avoid stalling — or, worse.