The death of "irreplaceable" Charlie Whiting has cast a shadow over the season-opening Australian Grand Prix in Melbourne.
Whiting, who carried out a wide range of duties as the FIA Formula One race director, died on Thursday from a pulmonary embolism in the southern Australian city where he was due to work this weekend.
News of the Briton's death filtered through the paddock at Albert Park on the eve of Friday's first practice session, with seminal figures from motorsport among those paying tribute.
Reigning world champion Lewis Hamilton said Whiting was an "iconic figure in the sport".
He added: "What he did for the sport and his commitment, he really was a pillar.
"I've known Charlie since I started in 2007... what he did for the sport, his commitment, he really was an iconic figure."
Four-time world champion Sebastian Vettel said he only spoke to Whiting on Wednesday.
He said: "You could ask anything at any time, his door was always open.
"He was a racer, he was just a very nice guy."
Christian Horner, team principal at Red Bull Racing, said Whiting was a man with "great integrity" and "performed a difficult role in a balanced way".
He added: "Charlie has played a key role in this sport and has been the referee and voice of reason as Race Director for many years.
"At heart, he was a racer with his origins stretching back to his time at Hesketh and the early days of Brabham.
"Charlie was a great man who will be sadly missed by the entire Formula 1 paddock and the wider motorsport community."
Former world champion Mario Andretti tweeted: "Totally shocking news of Charlie Whiting's passing. Charlie was a true Giant in our sport and very possibly irreplaceable. Sincere condolences to his family and everyone who appreciated this man. RIPmyfriend."
Several Formula One teams also paid tribute to Whiting after news of his death broke.
Renault described him as "one of the pillars and leaders of the sport," adding he "will be sorely missed".
The sentiment has been echoed by McLaren driver Carlos Sainz, Valtteri Bottas of Mercedes and George Russell, who competes for Williams.
It is expected the opening of the F1 season at Melbourne this weekend will include tributes to Whiting.
His four-decade career on the paddock started in 1977, working for Hesketh Racing. But his passion for the sport began at a much earlier date, stemming from fixing up cars with his brother at their home in Kent.
Whiting rose through the ranks to become essentially the sport's leading referee and, with more than 400 Grands Prix under his belt, part and parcel of the sport.
It was his uncompromising attitude to driver safety which earned him his reputation.
He would rigorously inspect circuits, checking a range of new tracks on the GP calendar for suitability, as well as looking at how safety could be improved within the car.
One of the more notable incidents in his career came stateside in 2005, when all but six drivers completed the United States Grand Prix owing to tyre concerns.
Concerns were raised about the safety of tyres brought by Michelin to the Indianapolis Motor Speedway. Whiting was asked to alter one of the corners which would allow seven teams to race safely.
He refused, leading to the farcical sight of 14 cars retiring after the parade lap. Writing to teams, he said it would be "grossly unfair to those teams which have come to Indianapolis with the correct tyres".
Whiting is credited with being among those who backed the introduction of the halo device, which helped Charles Leclerc avoid serious injury after a huge accident at last year's Belgian Grand Prix.
Speaking about his role in 2017 to Top Gear magazine, he said: "I still love it. The buzz is extraordinary. "It's rare I find myself thinking 'well, this is boring'."