Champion jockey Oisin Murphy is facing a six-month ban from the sport after testing positive for cocaine.
The news comes as a huge bombshell for racing, with one of their star names facing a lengthy suspension if found guilty.
The positive test for the Class A drug came at a July screening at a race meeting in France, and The Sun report that the 25-year-old has been providing hair samples to the French authorities for the past month, which have come back negative.
Oisin Murphy could face a six-month ban from racing after failing a drugs test for cocaine
Murphy, pictured riding at Newmarket last weekend, failed the test in France in July
It has been reported that Murphy is now waiting on the results of a B sample, but if found guilty he could face a huge ban from the sport. The jockey alleges his positive sample came from a night out.
There is a chance Murphy could then appeal a guilty verdict, which means any decision on a ban will be delayed until after British Champions Day on October 17.
That would leave British racing chiefs in a difficult position, with the rider then potentially lifting a trophy at Ascot under a cloud.
The Irishman is one of racing's biggest stars, and was crowned champion apprentice in his first full season of racing back in 2014.
Top jockey Murphy celebrates after winning on 'Alcohol Free' at Newmarket last weekend
Frankie Dettori is another jockey who has previously be handed a drugs ban after a failed test
He won 168 rides in 2019 and was crowned Champion Jockey.
Murphy would not be the first high-profile jockey to face a drugs ban, following on from Frankie Dettori and Kieren Fallon.
Fallon was slapped with a six-month ban in 2006 and then an 18-month ban in 2008 following a second failed test, while Dettori was sidelined for six months after a registering a positive sample in 2012.
In 2017, Robert Havlin was also handed a lengthy ban, spending nearly 10 months out of the saddle after a failed drugs test in France.