Tributes have been pouring in for Bob Torrance from the Open Championship at Royal Liverpool Golf Club as news of death emerged.
The inspirational coach, from Largs, North Ayrshire, died in his sleep, Sam Torrance said in a statement.
Torrance senior was best known for his work with two-time Open champion Padraig Harrington, who he tutored to both his Claret Jugs in 2007 and 2008.
But he had been battling cancer for some time and son Sam, a European Tour veteran and the 2002 Ryder Cup captain, announced he had passed away on Twitter on Friday evening.
"Sad day my dad just passed away peacefully in his sleep £reallygoingtomisshim," he said.
As well as Harrington, Torrance also coached his son and Paul McGinley among a host of others, but will be best remembered for his work with the former, who once described his coach as a 'genius'.
The pair were so close that Harrington used to stop at the family home in Largs with Torrance and his wife June, and following his first Open victory at Carnoustie the Irishman rang his mentor within 30 minutes of walking off the 18th green.
"Bob is the best swing coach in the world," Harrington said after successfully defending his title at Birkdale in 2008.
"You can see his genius in the way he can analyse any swing. He's spent his whole life examining the golf swing and his knowledge of cause and effect is just incredible."
Torrance, well known for putting long hours into his craft, was also known for speaking his mind and once lambasted former pupil Marc Warren, claiming he was more concerned with "big flats and Aston Martins" than developing his game.
Torrance was also a keen disciple of Ben Hogan and used to visit the nine-time major winner at his home in Fort Worth, Texas.
Warren learned the news of his death soon after completing his second round at the Open Championship at Hoylake.
The 33-year-old paid tribute, saying: "It is a sad day for golf, a legend has passed away. It is a sad day for everyone involved.
"He changed my career massively. I still to this day - and will for the rest of my career - use his teaching and his words of wisdom, the great stories that he had.
"He has been a massive influence on my life and my career and I can't thank him enough."
Warren credits Torrance for reviving his game and enabling him to compete at a high level.
He said: "He had a massive influence in my career and I might not be playing at this level if it was not for him.
"What they now understand about ball flight, Bob was teaching years ago. I cannot speak highly enough of him. He gave you absolutely everything he had to make you the best player you could possibly be. I will forever be in his debt for that."
Ian Poulter also paid respect, tweeting: "Really sad news Bob Torrance just passed away. An amazing man who coached so many great players. He will be missed."