Trainer Alastair Ralph confirmed that Treadwell was found dead this morning.
As well as still riding, he was assistant to the Bridgnorth-based Ralph, who described Treadwell’s death as “unbelievably sad” and a “big shock”.
Ralph told The Sun: “We found him this morning, it’s all still very raw. It’s just terrible, he had suffered depression and it was ongoing for a couple of years.”
Relive Liam Treadwell's finest moment in the saddle - the 2009 Grand National aboard Mon Mome
Venetia Williams has led the tributes to Treadwell who 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 in 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.
Nick Luck pays tribute to Liam Treadwell
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.
“He was here for a large part of his racing career, and not a day went by without him putting a smile on somebody’s face.”
The Injured Jockeys Fund released a statement on behalf of Treadwell’s parents, Mark and Lorraine, and his brother Nathan.
The statement read: “We are heartbroken that this has happened. We ask kindly that everyone respects our privacy in the coming days, so that we can begin to come to terms with our loss.”
I’ve know Liam Treadwell for 13 years and he was simply one of the kindest most sincere person I’ve ever had the honour of meeting just a huge loss to all of us that had the pleasure of knowing the great man, I’m heartbroken #Treaders— Aidan Coleman (@AidanColeman) June 23, 2020
Mick Fitzgerald - also a Grand National-winning rider having landed the Aintree spectacular aboard Rough Quest in 1996 - is a former weighing-room colleague of Treadwell's.
He told Sky Sports Racing: "Seeing him winning the Grand National is in many ways the best way to remember him.
"He was a really nice guy, he was a lovely rider - and it's just awfully sad. It's sad for his family and anybody connected with him. It just highlights again how precious life is.
"We used to call him 'Tredders'. He just got on with it when he was racing. You never knew he was there. He wasn't a shouter. He just wanted to do the best he could, and it's just awfully sad for everybody involved."
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."
Angus McNae and Gary O'Brien pay tribute to Liam Treadwell
Treadwell announced his retirement in 2018, but returned to the saddle the following year and had been riding with success again, while assisting Ralph with operations at his yard.
Treadwell rode more than 300 winners during his career and sprang one of the biggest surprises in the world’s greatest steeplechase when riding 100-1 outsider Mon Mome to victory in 2009 for trainer Venetia Williams, on his first attempt.
He was also third on Monbeg Dude in 2015.
Other big-race successes for Treadwell included the Grand Sefton Handicap Chase at Aintree on Bennys Mist in 2015 and the Byrne Group Plate on Carrickboy at the Cheltenham Festival in 2013.
Totally shocked and devastated to hear of the passing of Liam Treadwell . All our thoughts with his family and friends . So proud that we were lucky enough to have Liam as a key part of our team in the early days . RIP we will never forget you x A true gentleman. pic.twitter.com/cax304UoZf— Nick Gifford (@GiffordNick) June 23, 2020
Absolutely tragic news regarding Liam Treadwell. A lovely lad and brilliant jockey. All of our thoughts are with his family and friends at this sad time.— Jonjo O'Neill (@JonjoONeill) June 23, 2020
Terrible hearing the shocking news about Liam Treadwell. A kind, warm hearted man who I enjoyed having round Warren chase for the short spell he spent with us. May his mind now be at peace. Sleep well x— Olly Murphy (@OJmurphy91) June 23, 2020
The British Horseracing Authority's chief executive Nick Rust also paid tribute, saying in a statement: "We are devastated to hear the tragic news about Liam Treadwell.
"Liam had a fine career in British racing, riding over 300 winners in the 17 years that he held a jockeys' licence, obviously none more memorable than his remarkable 100-1 Grand National success on Mon Mome in 2009 - a ride that cemented his place in racing folklore.
"The racing community will be united in grief today, and the thoughts of everyone at the BHA are with Liam's friends, family and colleagues."
A statement released on behalf of the Injured Jockeys Fund and the Professional Jockeys Association read: “We were heartbroken to be informed this morning that one of our own, Liam Treadwell, has died. Tributes to Liam have rightly flowed in – given how universally popular, well-liked and respected he was – and the weighing room will be a lesser place for his absence.
“Liam will forever be remembered for winning the Grand National in 2009 on the 100-1 shot Mon Mome, trained by Venetia Williams. He was a gifted horseman, valued by racehorse trainers for both this and his communication skills.
“He 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. It is devastating that this has happened, and our thoughts and prayers are with Liam’s family, friends and everyone who knew and supported him.”
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