Whole of Europe risks spinning into crisis if leaders mishandle Brexit

France's Marine Le Pen likens Brexit to the collapse of the Berlin Wall. "It will be the beginning of the end. If Britain knocks down part of the wall, it's finished, it's over," she said. Whether she is right or wrong depends on the statecraft of Angela Merkel, Francois Hollande, Mateo Renzi and Poland's Beata Szydło.

A report this week by Morgan Stanley spells out the grim price Europeans will pay if they mishandle this event. Foreign investors would start to withdraw their $8.3 trillion of investments in the eurozone. There might be a bond run with Spain in the firing line.

The bank's base case for Brexit is that the MSCI Europe index of equities will fall 15pc-20pc, and 0.7 percentage points will be knocked off growth by late 2017. Its "high stress" scenario is a stock market crash of up to 30pc, a tightening in financial conditions by 200 basis points, severe contagion, and a 2pc blow to GDP that pushes the eurozone into recession, with "growing concerns around the sustainability of the entire European project". Whether the eurozone could withstand a fresh shock of this force is an open question...