For every tribute to the horsemanship of Guy Walter, there has been a salute to the kindness and sincerity of one of racing's true gentleman.

The sudden death of the 59-year-old horse trainer from a heart attack on Thursday has rocked the Australian horse racing industry, especially the Warwick Farm thoroughbred community.

A hands-on trainer, Walter saddled up runners at Randwick's midweek Kensington meeting and attended trackwork as usual on Thursday.

But shortly after, he suffered a fatal heart attack at his home.

Racing NSW chief executive Peter V'landys described Walter as a master horseman but an even better person.

"We can be champions in our field but you're always measured by the person that you are and he was just an absolute, kind human soul," V'landys said.

Stewards scratched his two runners from the Hawkesbury race meeting as jockeys and trainers paused for a minute's silence.

Joe Pride, whose stables are across the road from Walter's, said the trainer had been a mentor.

"He was a consummate professional. He was so patient with his horses and I'm proud to say I've modelled part of my training around Guy's approach and his patience," Pride said.

"I'm not just saying it because he's gone but I think he was the best trainer in Sydney."

Walter's formative years were spent with master horsemen Kevin Robinson and the legendary Bart Cummings and he strapped Think Big when the Cummings-trained stayer won the first of his two Melbourne Cups in 1974.

He earned a reputation as a consummate horseman in his own right and he did it without the benefit of an open cheque book at the yearling sales.

His first Group One win came in the 1995 Canterbury Guineas with Sharscay and it wasn't long after when Tie The Knot, one of modern-day racing's most popular horses, came along.

Tie The Knot won 13 Group One races, earning more than $6 million.

Walter also had a knack for getting the best out of fillies and mares but perhaps his career highlight was when he trained the trifecta in the 2005 Doncaster Handicap won by Patezza.

Blake Shinn, who rode the last of Walter's 36 Group One winners when Streama claimed last Saturday's Doomben Cup, led racing industry tributes on Twitter.

"Guy Walter was nature's kindest gentlemen. To be called his stable jockey was an honour. He was like a father to me and I'll miss him dearly," Shinn posted.