The man who sprang one of the biggest surprises in the history of the world's greatest steeplechase on 100-1 outsider Mon Mome 11 years ago has died at the age of 34.
Treadwell - known to many as Tredders - was born in Arundel and attended The Angmering School, and retained strong links in this part of the world.
During his career in the saddle he was a regular at Fontwell Park - famously winning on a horse called Royal Wedding on the day Prince William married Kate Middleton.
Venetia Williams, trainer of his Grand National winner, was among many in racing to pay heartfelt tributes to him. And Findon trainer Nick Gifford expressed his sorrow on Twitter, saying: "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."
Gifford was Royal Wedding's trainer and recalled that memorable day at Fontwell, adding: "Not a happy day for the bookies! But a joyous day for the team and Liam. Memories that last forever."
The Injured Jockeys Fund released a statement on behalf of Treadwell's parents, Mark and Lorraine and brother Nathan. It 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."
British Horseracing Authority chief executive Nick Rust said: "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 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."
Treadwell announced his retirement from riding in February 2018, but returned to the saddle in March 2019. He rode more than 300 winners during a career spanning 17 years.
West Mercia Police said officers were called to an address in Billingsley, near Bridgnorth, on Tuesday morning following the death of a man in his 30s. They added: "The death is currently being treated as unexplained. However, at this stage there is believed to be no third-party involvement."