Sterling flash crash had no single driver - BIS

October's blaze crash in sterling was brought on by a few elements - including the season of day - as per a report by the international banking body, the Bank for International Settlements.

In the early hours of 7 October, the pound fell by about 9% against the dollar - an abnormally large swing in two such widely traded currencies - before then largely recovering.

The BIS says there were no significant losses suffered by traders.

But it says lessons should be learned.

The BIS report, which drew on detailed analysis by the Bank of England, says the conditions for such a move were created by the lack of sterling dealers in the market at the time of day.

The trade took place in Asian markets, at a time of day when key sterling counter traders in London and other important Western markets are not operating.

Vulnerable

The BIS does not point to an actual event or piece of news for causing the crash, but reports at the time suggested a headline in the Financial Times quoting French president Francois Hollande pressing for a "hard Brexit", an outcome commonly thought to preclude a smooth transition, prompted some selling.

The flurry of trading, whatever the cause, included automatic deals.

Some of these were stop-loss orders - designed to simply sell a holding that has reached a price below which it will lose money for the investor - and algorithmic trades, which can be triggered by a host of factors, including, it is thought, certain types of news announcements.

The BIS said: "The report concludes that the time of day played a significant role in making the sterling foreign exchange market more vulnerable to imbalances in order flow.