Global stock markets have plunged after latest economic data spurred renewed fears of an economic slowdown - while at the same time the pound rose sharply on latest Brexit developments.
The FTSE 100 fell by 148 points, or 2%, in the biggest one-day decline since December - wiping £37bn off the combined value of its constituent companies.
In New York, the Dow Jones was 1.7%, or more than 400 points, lower at the time of the close in London, while markets in Germany and France also tumbled.
It came after data from Germany - a world exporting powerhouse - showed manufacturing shrank for the third month in a row in March.
Meanwhile, figures from the US pointed to slowing growth in factories as well as the service sector.
In currency markets, the pound was a cent higher against the US dollar at more than $1.32 after Theresa May won an extension to Brexit.
It rose by two cents versus the euro - weakened by the problems in Germany - to more than €1.17.
:: Sky Views: A decade after the banking crisis, we're no closer to normality
Analysts said sterling took strength from the Brexit delay as it removed the immediacy of a no-deal scenario next week.
However experts at Goldman Sachs revised up their forecast of the risk of Britain crashing out of the EU with no deal from 5% to 15%.
The pound's strength was one of the factors helping to drive the FTSE 100 lower on Friday, since it means weaker overseas earnings for its multinational companies.
Markets have become anxious in recent months about a cocktail of concerns.
They include the trade war between the US and China, the world's two biggest economies, as well as the US Federal Reserve's attempts to unwind stimulus measures it put in place after the financial crisis.
Earlier this week, the Fed said it was putting this tightening process on hold and that it anticipated no further interest rate hikes this year.