Black Monday: 25 years on
19 October 2012 Last updated at 13:51 BST
In October 1987, stock markets around the world collapsed. Months and years of share price rises were reversed in just one day of trading.
Yet, unlike the more recent crisis of 2008, 25 years ago, the world economy seemed to shrug off the falls. Our business correspondent Jonty Bloom was there on the day, and reflects on Black Monday.