The FTSE 100 Index fell 117.9 points, or 2.1%, to 5533.9 amid worries that a raft of Spanish regions were poised to ask for government bailout funds, increasing the likelihood that the country itself will turn to the EU for help.
The fall wiped nearly £30 billion from the value of London's leading shares index, with all 100 companies losing value and banks falling up to 4%.
More top news
The Cosby Show star, 80, was found guilty of three counts of aggravated indecent assault.
The Government's stance risks a negotiating car crash with the EU, as it refuses to acknowledge risks over the Irish border.
Sunshine and a soaking