Venetia Williams has led the tributes to Liam Treadwell following the Grand National-winning jockey's death at the age of 34.
Treadwell sprang one of the biggest surprises in the history of the world's greatest steeplechase when steering 100-1 outsider Mon Mome to victory in 2009 for the Williams yard on his first attempt.
Williams said: "It's a massive shock. I think we all thought he was in a good place now, having been through some tough times in previous years.
"We thought his renewed career had put him in a situation where he was happy. It's desperately sad news."
Other big-race successes for the Treadwell-Williams combination included the Grand Sefton Handicap Chase at Aintree with Bennys Mist in 2015 and the Byrne Group Plate with Carrickboy at the Cheltenham Festival in 2013.
But it was that day at Aintree 11 years ago that stands out for Williams, who added: "We shared a day that was certainly the best day of my life, and I suspect of his.
"Liam rode many winners for us, but over and above that he was such a lovely person and, ironically, always such a happy person. I remember Dandy Nicholls ringing me up many years ago to tell me about this young lad who thinks he can do the weight on the Flat, but he can't, and he wants to come to you to ride over jumps.
"Not a day went by without him putting a smile on somebody's face."
Treadwell announced his retirement from riding in February 2018, but returned to the saddle in March 2019 - riding more than 300 winners during his career.
As well as still riding, he was assistant to Bridgnorth-based trainer Alastair Ralph, who described his death as "unbelievably sad" and a "big shock".
The Injured Jockeys Fund released a statement on behalf of Treadwell's parents, Mark and Lorraine, and brother Nathan.
The statement read: "We are heartbroken. We ask kindly that everyone respects our privacy, so that we can begin to come to terms with our loss."
A statement from West Mercia Police read: "Earlier this morning police were called to an address in Billingsley, near Bridgnorth, following the death of a man in his 30s.
"The death is currently being treated as unexplained. However, at this stage there is believed to be no third-party involvement."
A statement released on behalf of the Injured Jockeys Fund and the Professional Jockeys Association read: "Liam was polite, funny, kind and brave, having spoken passionately and eloquently about his mental health issues both in the press but also in our own 'Jockey Matters' films."