How to win £45m in a few minutes

28/12/2016 | By | Reply More

Five years ago today we were treated to a day of spectacular proportions!


We are now out of the Kempton meeting and into a quieter period, but Leopardstown brings us the key targets of the day and is worthy of a look. I’m less convinced by other markets.

Today the two big races are the Lexus chase and the Christmas hurdle. The meeting overall has prize money of £145k which is more than all the other meetings combined.

Leopardstown 2011

On this day at the Christmas hurdle at Leopardstown, something went very, very wrong. The exchange is the epitome of fairness. You lodge money upfront to place your bets and all bets are honoured. With a third party bookmaker there are reasons not to pay out but not on the exchange. You see a price, you can take it safe in the knowledge that it will be honoured.

Christmas hurdle 2011

In a fairly standard race, Voler La Vedette ran home to take the win. Nothing unusual about the win, but for most of the race £21m was available to back at good odds. Remarkably as the horse pulled away to stride past the post you could still back it at odds of 29, not only that you could do it for incredible amounts of money.

There was so much money that nobody it seemed was able to take all that money in-running. ‘Only’ £1.6m was matched, meaning the loser would have to pay out a cool £44.8m to the backers. It seemed too good to be true and unfortunately it was the market was never paid out.

A full explanation was never made, though I did I post a few plausible theories. When we looked at the data we could see, honestly by coincidence, that the amount of money that was being offered was the maximum positive value for a 32-bit signed integer. For the less technical amongst you, the maximum amount allowed by some computer systems. Was this the cause? Some really obscure bit of code, a lack of error trapping or a weird database issue. Most likely, but I guess the reason for not offering a full explanation was to avoid future exploits? Since then the API and the infrastructure behind the exchange has changed significantly. So I am guessing that this exploit probably doesn’t exist anymore. But it was a ‘funny’ thing to see.


Everything went into melt-down that day. For the full story, you need to read the full blog posts, but also the forum posts for the race. I’ve listed them all for your enjoyment. It will be a day never to forget!

Here are a full lists of what happened on that day: –

  1. Bet Angel forum posts
  2. Biggest ever loss on Betfair?
  3. How to lay £600m worth of bets on Betfair
  4. £1k account caused £600m of error

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Category: General, Horse Racing

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