Top jockey Ryan Moore is to miss the final two days of Newmarket's July meeting with a neck injury.
The 31-year-old was hurt on the opening day of the meeting, on Thursday, when his horse became trapped in the stalls.
Moore, who rode a record nine winners at Royal Ascot last month, stayed in hospital overnight and was set to have a scan on Friday.
Agent Tony Hind said: "He feels fine in himself and is in good spirits but won't be riding over the weekend."
The horse, Newton's Law, appeared to be uninjured in the incident, which happened ahead of the day's final race.
Moore, a three-time flat racing champion jockey, is leading this season's jockey standings.
He was scheduled to have seven rides at Newmarket on Friday.