Unseeded British star Laura Robson was matched at 12.5n/a in the Betfair market before overcoming Petra Kvitova in the second round of the Aussie Open, with the number eight seed matched as low as 1.081/12.
More than £18.5m was matched on the Betfair Match Odds market as Robson emerged victorious from what was an epic late-night encounter in Melbourne.
The British number two beat former Wimbledon champion Kvitova 2-6 6-3 11-9 in a match that did not finish until 00:30 local time.
Robson, who is now priced at 120.0119/1 to win the tournament from a high of 600.0599/1, recovered from 3-0 down in the final set to set up a third round clash with 29th seed Sloane Stephens.
The Brit will be looking to at least match her run at last year's US Open, where she beat Li Na and Kim Clijsters on her way to the last 16.
Elsewhere in the third round, Britain's Heather Watson takes on Agnieszka Radwanska while former finalist Venus Williams faces 2008 champion Maria Sharapova.