Britain-based jockey Frankie Dettori faces a drugs hearing in Paris which could have a huge impact upon his career as one of Europe's most successful riders.
The Italian, the 'face' of British flat racing, tested positive for a banned substance at Parisian course Longchamp on September 16.
He now face a hearing on Tuesday before the medical committee of France Galop, French horse-racing's ruling body.
If found guilty, the 41-year-old Dettori could face a minimum six-month ban which would be upheld by other racing authorities worldwide.
Christopher Stewart-Moore, Dettori's lawyer, told the BBC last week his client had not been seeking any competitive advantage over his rivals.
"There are a large variety of substances which are banned by France Galop," Stewart-Moore said.
"We are not going to say which substance he has tested positive for as that would be in breach of their rules, but it's not a performance-enhancing drug."
Dettori had four rides at the Prix de l'Arc de Triomphe trials meeting.
He rode Joshua Tree to finish third in the Prix Foy, Sarah Lynx who trailed home last in the Prix Vermeille, then Farhh who was beaten by a head in the Prix du Moulin and Willing Foe, another Godolphin charge, who came in third in the Prix Gladiateur.
It was after the ride on Farhh that he failed the doping control.
News of Dettori's failed test came three weeks after he split from Dubai-based Sheikh Mohammed's Godolphin set-up, which provided him with several major race winners in an 18-year association.
In 1993 Dettori was stopped by police on London's Oxford Street and a small quantity of cocaine was found in his car.
He escaped with a caution but the incident cost him a lucrative two-year contract to ride in Hong Kong.
"It was the kick up the backside I needed," he admitted afterwards.
Dettori, married with five children, went on to scale the heights of his profession, winning all five English Classics and three-times triumphing in France's Prix de L'Arc de Triomphe, Europe's most prestigious race.
In 1996 he made history by riding all seven winners during a day's racing at Ascot, south-west of London.
He is not the first British-based jockey to fall foul of French racing's doping rules.
In 2006 six-time British champion Kieren Fallon was banned for six months after testing positive for a metabolite of a prohibited substance.
The following season he failed a control for cocaine at Deauville racecourse and was suspended for 18 months.
Former top British jump jockey Dean Gallagher was found with the recreational drug in his system on three separate occasions in France in 2000, receiving a six-month ban.