Jamie Spencer and The Lark were very easy winners of what was a dramatic DFS Park Hill Stakes at Doncaster.
Entering the final two furlongs of a race known as the fillies' St Leger, Seal Of Approval came down and sent jockey Hayley Turner crashing to the floor.
The Lark, the 15-8 favourite, was third in the Epsom Oaks and put a fifth-place finish at Saint-Cloud behind her as she beat Phiz by a cosy length and a quarter.
The winner is trained by Michael Bell, who has had a long association with Turner.
He said: "It's a dreadful thing to happen, Hayley has been a great friend and I hope she's alright.
"This is a lovely filly and she'll make a great mare at stud for the owners one day.
"She should get better next year and hopefully we'll get the ground for her on Champions Day for the Qipco Fillies fillies' race."
Turner, 30, was taken to Doncaster Royal Infirmary for further assessment.
Course officials said the leading female rider was conscious and that she had gone to hospital as a precaution.
She is not thought to have suffered any serious injuries from an appalling-looking accident which drew sharp gasps from the grandstand.
Turner had only just returned to action after she sustained a broken ankle at Yarmouth in July.