Seven people have been arrested following a track invasion at the beginning of the British Grand Prix at Silverstone.
The protesters walked onto the track to demonstrate against global oil usage, and sat down on the tarmac.
Before the risk police said they were aware of plans to stage a protest at Britain's biggest weekend sporting event.
The cars had been traveling slowly because the race had been red flagged after a serious crash involving Alfa Romeo's Zhou Guanyu and Williams' Alex Albon.
No one was seriously injured in the crash.
In an instagram post after the race, Lewis Hamilton said while he loves people fighting for the planet they should not put themselves in danger.
Hamilton said: "As we've seen today, this is a very dangerous sport. I wasn't aware of the protests today, and while I'll always support those standing up for what they believe in, it must be done safely.
"Please don't jump on to our race circuits to protest, we don't want to put you in harms way."
Northamptonshire police's event Commander Chief Inspector Tom Thompson said he was very disappointed that people had ignored warnings about protesting at the event.
He said: "We offered to facilitate a peaceful event at the circuit but they instead chose to put the lives of the drivers, marshals and volunteers at risk. It is incredibly disappointing that anyone would make the decision to do this.
“Thankfully we had plans in place for an eventuality such as this and the group were swiftly removed and arrested by our officers."
Seven people were custody and were being questioned about the protest.
Ferrari's Carlos Sainz won the race, with Red Bull's Sergio Perez and Lewis Hamilton second and third respectively.
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