European stock markets have slumped after Donald Trump’s second reversal on tariffs caused deep uncertainty among investors, while the euro was on track for its biggest weekly rise since the financial crisis. Germany’s Dax index dropped by 1.6%, as weak factory data added to the signs of difficult economic conditions. France’s Cac 40 fell by 1.2%, while London’s FTSE 100 dropped by 0.5% on Friday morning, after the US benchmark S&P 500 index fell 1.8% on Thursday night to its lowest level since early November. The FTSE 100 was on track for its worst week in a year, while the…