Police say they have uncovered evidence that protesters are planning to invade the track during Sunday's British Grand Prix.
Officers policing the Formula 1 showpiece at Silverstone reported receiving "credible intelligence" that campaigners are plotting to get on the track during the race.
They have now issued a warning for them to think again - and asked the public to be vigilant for anything that doesn't look right.
Ch Insp Tom Thompson, the event commander, said: “We have received credible intelligence that a group of protestors are planning to disrupt the event and possibly invade the track on race day.
“First of all, I want to appeal directly to this group of people and strongly urge you to not put yourselves, the drivers, as well as the many marshals, volunteers and members of the public, at risk.
“Going onto a live racetrack is extremely dangerous – if you go ahead with this reckless plan you are jeopardising lives."
He said police this weekend would be happy to help "facilitate a peaceful protest" if protesters made contact.
The British Grand Prix was famously interrupted in 2003 when Fr Cornelius Horan walked on to the track to publicise his belief that the end of the world was coming. The following year he interrupted the marathon at the Athens Olympics.
Northamptonshire Police has drafted in extra resources for the weekend, during which 400,000 people will attend the track over the three days.
Ch Insp Thompson said the force was not complacent, adding: "The security measures we have put in place are as stringent as ever and anyone thinking of taking advantage of the race weekend to commit a crime will be caught.
He said: “Finally, I would just appeal to members of the public to be extra vigilant and to make us aware of anything you see during the race weekend that doesn’t look right."
The run-up to the weekend has been mired in controversy after racist comments made by former world champion Nelson Piquet came to light.
Hamilton then hit back at "archaic mindsets" and, following 91-year-old Bernie Ecclestone's comments in support of Vladimir Putin, questioned why "older voices" were being given a platform in the sport.
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