Bookies are set to pay out millions after "a weapons-grade coup" involving four horses – all with links to Northern Ireland's most famous punter, Barney Curley.
The alarm bells began ringing for bookmakers early yesterday when money began pouring in for Eye Of The Tiger, Seven Summits, Indus Valley and Low Key.
All four horses were returning from long absences off the track and Seven Summits was the only one to have shown any inkling of form.
At overnight prices, an accumulator on the four horses was paying in excess of 9,000-1.
However, by the time the races began the odds were only 17.5-1 as punters caught on and bookmakers moved to limit their potential payouts.
The gamble got off to a flying start when the 1.30pm at Lingfield was won by Eye Of The Tiger – on its first run in 480 days – which was backed from 4/1 to Evens.
Ten minutes later the bet became a reality when Seven Summits romped home in the 1.40 at Catterick.
All eyes then turned to Kempton where Indus Valley, which was a massive mover from 10/1 to 4/6, made it three on the bounce before the ironically named Low Key delivered the killer blow in the 6.25pm at Kempton.
A spokesman from Paddy Power bookmakers said: "This is a weapons-grade coup."
Feilim Mac An Iomaire said they estimated a loss of over a million pounds.
"No-one is going to be playing any violins for the bookies but we genuinely had our pants pulled down, it's the nature of the industry and we really have to take our hats off to the punters who have gotten the better of us today," he said.
Pat Cooney, a spokesman for Bet365 bookmakers said: "It's still going to be a bad day for us but very few people were quick enough to get the good odds that were initially available about some of these horses.
"Thanks to online social media, nothing seems to be so much of a secret these days. We'd certainly like the last 24 hours back, that's for sure, but we'll still be in business tomorrow."
There is no suggestion of any illegal activity but the British Horseracing Authority said it would investigate the circumstances.
Curley – a veteran of successful betting coups - could not be contacted for comment.
Curley famously masterminded the Yellow Sam betting coup – one of the largest betting coups in Irish history – at Bellewstown racecourse in Meath in 1975.
He did nothing illegal, and the bookmakers were forced to pay out IR£300,000 – which they did in single notes that filled 108 bags.