Coral suspended betting on the abdication, the Independent reported. Someone wagered 200 pounds ($330).
"We rarely see betting over 20 pounds, so the 200-pound gamble was a red flag for us," a Coral spokeswoman said. "Bets about the royal family placed in the Windsor area [area] usually spot on, which suggests this could be a case of insider information."
Coral had already shortened the odds on the queen's abdication from 3-1 against to 1-2 in the wake of news that her media operation and Prince Charles' are being merged.
At 87, the queen remains active and apparently healthy, keeping up a busy schedule. But she has handed over more duties to the prince of Wales in recent years, and he represented her last year at the Commonwealth heads of state meeting for the first time.
In the Dutch royal family, abdication has become routine with Queen Beatrix stepping down last year when she turned 75. In Britain, the decision by the queen's uncle, Edward VIII, to give up the throne to marry a U.S. divorcee has made abdication less attractive.