The FTSE 100’s largest single-day percentage fall during the 1987 global crash was 12.2%.
London shares plunged on October 20, 1987, the day after Wall Street’s Black Monday. The FTSE 100 fell 12.2%, reflecting the international spread of the panic. Markets in Asia and North America had already experienced severe declines, and investors worldwide were reacting to rapidly changing prices and uncertainty.
The 1987 crash was unusual because share prices fell extremely quickly without a matching collapse in the real economy. Concerns about valuations, international trade, interest rates, and computerized trading all contributed to the selling pressure. Portfolio insurance strategies could also amplify downward moves.
The FTSE 100 recovered over time, although market volatility remained intense. The event helped encourage reforms such as trading halts and circuit breakers. The 12.2% figure concerns the index’s percentage change on that particular trading day; it is distinct from the Dow’s 22.6% fall on October 19.