John Button, father of 2009 world champion Jenson and a popular presence in the Formula One paddock, has died of a suspected heart attack aged 70.
The McLaren driver's agent said in a statement that the body was found at home in the south of France by a friend on Sunday.
McLaren team principal Martin Whitmarsh mourned a "unique and...irreplaceable part of the McLaren family" while drivers and bosses paid fond tributes to the Briton.
"In my long Formula One career, I've encountered many drivers' fathers, but I think it's safe to say that John was perhaps more devoted to his son than any of them," said Whitmarsh.
"Ever since Jenson was a boy, racing go-karts, his dad has been at his side, helping him, supporting him, finding the money for the next race.
"As Jenson grew older, and continued to win in cars, still John was always there, his most steadfast helper and supporter."
Button senior enjoyed a successful career of his own in rallycross before devoting himself to his son's career, also preparing go-karts for others including Lewis Hamilton, who went on to become 2008 world champion and a McLaren team mate.
In Formula One, he attended almost all of Button's 249 races and could usually be found in the team hospitality, happy to stay in the background with a glass of wine close to hand while supplying a steady stream of entertaining motor racing tales.
"Without Dad, I probably would never have got into motorsport," Button said in an autobiography ghost-written after his 2000 debut season with Williams.
"Throughout those early years he was the one standing out there in the rain while I was on the track having all the fun."
Image: John Button
Photograph: Mark Thompson/Getty Images