For nearly 15 years, a HK$100 million horse racing jackpot—the largest the city had ever seen—remained a tantalizing mystery. The winning ticket, which correctly predicted the top three horses in three different heats, was never claimed, fueling speculation across the city. The prize money was eventually donated to charity, but the public remained in the dark about the identity of the mysterious winner.

Now, a recent investigation by Bloomberg News has finally put the pieces together, revealing the man behind the bet to be William “Bill” Benter, a Pennsylvanian mathematician widely regarded as the most successful horse racing gambler of all time.

The incredible jackpot, which had rolled over six times, was a feat with over 10 million possible combinations. But for Benter, it was a calculated play. A decade earlier, the math-whiz had moved to Hong Kong and started applying his skills to the horse racing track. He created an algorithm that could balance more than 120 variables per horse—including its diet, the weather, and its past performance—to calculate its near-exact chance of winning.

This systematic, data-driven approach allowed Benter to turn a profit on a sport thought to be entirely unpredictable. While he is secretive about his exact winnings, his net worth is estimated to be close to $1 billion.

The decision to leave the record-breaking prize unclaimed was not a fluke. It was a conscious choice by Benter, who according to sources, anonymously instructed the Hong Kong Jockey Club to donate the funds to charitable trusts. His action was a final statement, proving not only the efficacy of his system but also his disinterest in the monetary value of a single win. As a result, a city’s mystery has been solved, and a gambler has entered the annals of history not just for his genius, but for his quiet generosity.