Tensions between the United States and Iran show little sign of easing following Tehran’s shooting down of a U.S. military drone last week. U.S. President Donald Trump halted retaliatory air strikes against Iran at the eleventh hour. This week the European Union’s foreign policy chief Federica Mogherini heads to Washington to discuss the crisis and will likely come under intense pressure over Europe’s support for the 2015 nuclear deal with Iran. Henry Ridgwell reports from London.