There is a number that still haunts risk officers. It is not a particularly elegant number, and it has no special mathematical properties. But in the world of financial controls, it carries the weight of a cautionary tale told at every induction, every audit, every training day that has happened since February 1995.

The number is 88888.

It was an account code — the designation of a secret “error account” opened by a young derivatives trader named Nick Leeson at Barings Bank’s Singapore operation in 1992. By the time anyone in London thought to look at it properly, the account had swallowed £827 million. The bank had been alive for 233 years. It survived the Napoleonic Wars, two world wars, and the Great Depression. It did not survive account 88888.

The Setup: A Boring Job in Singapore

Leeson arrived in Singapore in 1992 with a mandate that was supposed to be straightforward and low-risk. His job was to arbitrage Nikkei futures — exploiting tiny price differences between the Singapore exchange (SIMEX) and the Osaka exchange (OSE). The positions were supposed to net out to near-zero exposure. It was a steady, unremarkable business.

But Barings made a decision that would later look almost unbelievably careless. They allowed Leeson to run both the trading desk and the back office that was supposed to check his trades. He was, in the language of financial controls, the player and the referee simultaneously.

Account 88888: The Black Hole Opens

The account was opened innocuously enough. A junior member of Leeson’s team made a £20,000 error — a small but real loss that should have been reported to London. Leeson buried it instead, in an existing error account he designated 88888. Eight is a lucky number in Chinese culture. The irony is not subtle.

What followed was not a criminal mastermind’s plan. It was the gambler’s logic, applied with increasing desperation. Each unauthorised loss was covered by a bigger unauthorised bet, and each bigger bet required the books to be adjusted to conceal it. Because Leeson controlled the records, London saw only the profits he fabricated. He became their star trader.

The Kobe Earthquake and the Death Spiral

By late 1994 the hidden losses topped £200 million. Leeson bet bigger: options that paid off only if the Nikkei stayed calm. Then the Kobe earthquake hit on 17 January 1995. The Nikkei collapsed. Instead of cutting losses, Leeson bet the entire bank that the market would rebound. It didn’t.

By late February the losses hit £827 million — more than all of Barings’ capital. Leeson left a note reading “I’m sorry” and ran. Days later, the 233-year-old bank was sold to ING for £1.

The Lesson It Died For

The controls failure at the heart of Barings is almost insultingly simple to state: never allow the same person to both place trades and maintain the records that verify those trades. Segregation of duties is not a bureaucratic nicety. It is the single most effective control in financial operations, and its absence is the precondition for virtually every rogue trader scandal in history.

And yet Société Générale lost €4.9bn the same way in 2008. UBS lost $2.3bn in 2011. The names change. The flaw doesn’t.