The 'wrong horse' who won a race at Yarmouth at odds of 50-1 has been disqualified by the British Horseracing Authority and her trainer fined £1,500.
Two-year-old Mandarin Princess, trained by Charlie McBride, was declared the winner on 27 July after beating Fyre Cay.
But a scan afterwards identified the horse as three-year-old stablemate Millie's Kiss, who had been due to run in a later race at the same course.
McBride said it was an "honest error".
The result officially stands for betting purposes, but some bookmakers said they will pay out on the horses finishing first and second.
McBride has reportedly said he will use £600 he won backing Mandarin Princess each way at Yarmouth towards the fine.
"Most of the runners you run you hope would run well so as support for the horse you'd put £10 each way, or £5 each way," he is quoted as saying outside the hearing.
"In this case I had £10 each way and was hoping she might scrape into the first three as a fun bet. That's all. The fine's £1,500, so I'm still £1,000 out of pocket."