Cheltenham Festival-winning jockey Danny Cook will face an inquiry after testing positive for cocaine.
The 31-year-old rider has accepted an interim suspension and will miss the big meeting next month.
In a statement, the Professional Jockeys' Association (PJA) confirmed he tested positive for the drug.
Cook, who was set to ride for trainer Brian Ellison at Cheltenham, apologised to "all those he has let down through an act of foolishness".
The British Horseracing Authority (BHA) has scheduled a hearing for 19 March, with the jockey facing a ban of about six months if he is found to have breached the rules.
Meanwhile, Irish jockey Mark Walsh will miss the Festival after breaking his arm in a fall during Thursday's meeting at Thurles.
Walsh's agent Garry Cribbin confirmed the length of the jockey's absence in a tweet: "Mark Walsh has a clean break on his arm and will have a plate put in tomorrow. Out of action for six weeks."
As well as missing the Cheltenham Festival from 10-13 March, Walsh could also miss the Aintree Grand National and the Irish Grand National at Fairyhouse, both in April.