McLaren boss Ron Dennis led the tributes to Professor Sid Watkins as news of the F1 doctor's death rocks the sport.

"Today the world of motor racing lost one of its true greats: Professor Sid Watkins," said Dennis. "No, he wasn't a driver; no, he wasn't an engineer; no, he wasn't a designer. He was a doctor, and it's probably fair to say that he did more than anyone, over many years, to make Formula 1 as safe as it is today.

"As such, many drivers and ex-drivers owe their lives to his careful and expert work, which resulted in the massive advances in safety levels that today's drivers possibly take for granted," he continued. "But, more than that, Sid was a dear friend of mine, and I'll miss him bitterly.

"To his widow Susan, and to his family, I extend my sincerest condolences. He was a truly great man, and the world of motor racing simply won't be the same without him."

Among the first to react was Rubens Barrichello, whose horrendous crash during Friday practice at Imola in 1994 was to mark the beginning of one of the blackest weekends in the sport's history.

"It was Sid Watkins that saved my life in Imola 94," he Tweeted. "Great guy to be with, always happy... tks for everything u have done for us drivers. RIP."

"RIP Prof. Sid Watkins. Sad news for us who stay behind," added Senna's nephew Bruno.