A volunteer marshal has died in an accident during a race at Brands Hatch motor racing circuit.
A racing car crashed, hitting two people on the track at about 15:00 BST on Saturday, Kent Police said.
A man in his 60s, from Surrey, died at the scene. The second person and the car's driver were taken to hospital for treatment.
On social media Lewis Hamilton said he was "devastated" to hear of the marshal's death.
He posted on Instagram: "Devastated to hear of the passing of a marshal at the Brands Hatch Circuit.
"These volunteer marshals are what makes racing possible, they are heroes.
"My heart is with his family."
A minute's silence was held on Sunday morning, with a crowd gathering on the track to pay their respects.
An investigation into the accident at the track in West Kingsdown has begun.
The rest of Saturday's racing activity was cancelled, but it resumed on Sunday.
One of the drivers, Alan Greenhalgh, said after a Sunday win at the track: "We're so desperately upset about yesterday, and it's a bit of a hollow victory really.
"Without the marshals we wouldn't be racing at all.
"Condolences, and our thoughts are with the family."
In a statement the British Automobile Racing Club (BARC) said: "On behalf of everyone connected with the BARC, we are devastated by [the] loss of one of the amazing volunteer marshal community who do so much to enable the sport to take place.
"Our thoughts and best wishes are with the family and friends of all those involved."
Police said there were no suspicious circumstances and officers were working with motorsport authorities to compile a report for the coroner.
Motorsport UK said: "The thoughts of everyone at Motorsport UK are with the marshal's family, the event organisers, and other members of the motorsport community present."
Among the races scheduled for the weekend were events for the Britcar Endurance Championship, Classic Touring Car Racing Club, Kumho BMW Championship and Junior Saloon Car Championship.
Last week British superbike rider Brad Jones was placed in an induced coma after crashing at Brands Hatch.