Formula One race director Charlie Whiting has been described as "very possibly irreplaceable" after his unexpected death in Melbourne on the eve of the opening grand prix of the 2019 season.
Whiting, one of the sport's most influential men and a beloved figure on the circuit, suffered a pulmonary embolism on Thursday morning.
The Englishman was 66.
With more than four decades experience in F1, Whiting was the authoritative figure for rules and technical regulations, and a crucial link between teams and the governing body.
Drivers old and young, from the very top of the sport to those attempting to forge their names, paid their respects.
Reigning champion Lewis Hamilton described him as "a pillar" and an "iconic figure" for the sport.
Ferrari legend Sebastian Vettel walked the Albert Park track with Whiting on Wednesday. He said the loss was "difficult to grasp".
"I have known him for a long time. His door was always open. The whole paddock, the whole F1 family's thoughts are with his family," Vettel said.
Whiting began his 42-year motorsport association in 1977 with Hesketh Racing.
He would become chief mechanic at Bernie Ecclestone's Brabham team and helped Brazilian star Nelson Piquet to win F1 championships in 1981 and 1983.
Whiting joined the governing body soon after and rose to become race director, overseeing safety and sporting matters; all while remaining a popular figure amid the white-hot competitiveness of the series.
Mario Andretti, the 1978 world champion, described Whiting's death as totally shocking.
"Charlie was a true giant in our sport and very possibly irreplaceable. Sincere condolences to his family and everyone who appreciated this man," he Tweeted.
Whiting's death will severely impact the running of the Australian Grand Prix.
Grief-struck FIA officials spent the day making contingencies for the many roles Whiting was set to conduct over the weekend; from drivers' briefings to counting down the start of the race.
FIA president Jean Todt said Formula One had lost "a faithful friend and a charismatic ambassador".
"I have known Charlie Whiting for many years and he has been a great race director, a central and inimitable figure in Formula One who embodied the ethics and spirit of this fantastic sport," Todt said in a statement.
Australia's sole representative in Sunday's race, Daniel Ricciardo, spoke for all drivers when he said the teams would be giving their best efforts across the weekend in tribute.
"He was there for us. We (drivers) would give him a hard time but he was always receptive, you always felt he was on our side," he said.
"I am sure we will all race with a lot of passion this weekend (for Whiting)."