Kieren Fallon has retired from racing aged 51 due to an ongoing battle with depression.
The Irishman is a six-time champion jockey and a winner of 16 British Classic races, including three victories at the Derby - the most recent of which came atop North Light in 2004.
Fallon had linked up with Curragh trainer Michael O'Callaghan this season, but Turf Club chief medical officer Dr Adrian McGoldrick confirmed Fallon's intention to step down from the saddle.
"Kieren is suffering from severe depression. When he came to me before getting his licence to ride this year it was clear he was suffering from depression and I treated him with anti-depressants," McGoldrick said in quotes reported by The Racing Post.
"He told me that he hadn't intended to make a comeback but decided to do so having been encouraged by Michael.
"But he rang me last week and said his situation had got worse. I met him and on Sunday he told me he didn't feel strong enough to speak to anyone in the media about his situation and asked me to speak on his behalf.
"He told me that he has lost the motivation to continue his riding career and wanted people to know about his decision to retire. He said it was time to move on once his depression has been managed.
"In recent years he found himself suffering from profound fatigue but nothing physically wrong was found when doctors examined him."
Fallon has also won the Prix de L'Arc de Triomphe twice and counts 30 winners at Royal Ascot on his impressive CV.
His career has not been without controversy, though. In December 2007 a judge ruled he had no case to answer against accusations of race-fixing, while Fallon has twice served bans for drug offences.