Police have increased their patrols at the MotoGP British Grand Prix at Silverstone this weekend as a result of the increased terror threat nationally - but have stressed there is no specific threat to the event.
A spokesman said there would be more officers and they would be more visible as they carried out checks both at the circuit and at campsites.
Visitors to the site were urged to be vigilant and report any suspicious activity as soon as possible.
"You will be aware that, in the past 24 hours, the Home Secretary has raised the threat level to the UK from international terrorism to Severe, meaning an attack is highly likely - this applies to the UK as a whole not a specific area.
"Please be reassured there is no specific threat, however, security and policing at the event will be enhanced and more visible, and race goers will see an increase in security and policing presence during the weekend."
Bosses at Silverstone racing circuit said they were disappointed to have lost the MotoGP British Grand Prix - but that extending their contract did not make financial sense.
The circuit said it had invested heavily to develop its site specifically to host both the Moto GP championships and Formula 1 and had helped to make the series a successful event.
But Richard Phillips, managing director of Silverstone Circuits Limited, said it could not come to an agreeing with the Dorna, the event's rights holders.
“We have expressed our desire to keep MotoGPTM at Silverstone, but the event is not sustainable at the fee level Dorna was proposing.
"Any future deal had to make economic sense and sadly we reached an impasse. The Circuit of Wales obviously believes it can make the finances work.”
But the circuit has not rule out hosting the British Grand Prix next year while the event waits for the Circuit of Wales to be completed.
"A venue for 2015 needs to be agreed as soon as possible to avoid having a negative impact on the success of next year’s British Grand Prix.
"Silverstone remains the ideal venue to stage MotoGP.
"Last year’s record crowds are testament to the excellent British Grand Prix experience provided by Silverstone."
Silverstone has lost the contract to host the British Grand Prix of the MotoGP.
The event will take place at the Northamptonshire circuit next month.
But now a five-year deal has been signed to hold future meetings at the not-yet-built Circuit of Wales, which will be near Ebbw Vale in South Wales.
It will host its inaugural event in 2016 with MotoGP's official website suggesting next year's British Grand Prix could take place at yet another venue.
Since the beginning of the British motorcycle Grand Prix in 1977, only the courses at Donington and Silverstone have been used.
Silverstone has come to the end of its own five-year deal.
The Circuit of Wales could have its contract extended by a further five years if the deal proves to be a success, meaning Silverstone would have to wait until 2024 to bid again for the event.
Tributes are being paid to a veteran racing driver who was killed when his car rolled over during a classic car race at Silverstone over the weekend.
Denis Welch, 69. died after the accident during a race for pre-1966 Grand Prix cars.
Brother-in-Law Bryan Downes pays tribute to Denis Welch who died during this weekend's Silverstone Classic.
Pictures have been released of the man who died at the Silverstone Classic meeting at the weekend.
Denis Welch from Staffordshire was driving a 1960s sportscar during the event.
Mr Welch ran a motor spares business for classic cars.
A man has died while driving at the Silverstone Classic. He's been named as Denis Welch.
Eyewitnesses say the accident was on the "first lap" event which meant the cars were going fairly fast but this happened as the cars bunched together at the hairpin bend ahead of the Wellington Straight.
It's estimated the cars had slowed considerably at this point and were doing no more than 30mp but two touched and one vehicle rolled over.
1960s sports cars do not have the safety equivalent of their modern counterparts and are inherently more dangerous to drive.
The Silverstone Classic event is believed to be the world's biggest classic sportscar race gathering and organisers say there has not previously been a fatality during its 24 years.
A spokesman for Silverstone Classic said "The event organisers, the race organisation, and the circuit’s medical and emergency services, will all now be co-operating with the Police and the MSA, the UK official motor sport governing body, to conduct a full investigation. All those involved in the event offer sincere condolences to family and the friends of Denis Welch at this very sad time."
A spokesman for Silverstone Classic has confirmed that a participant in this weekend's event had died following a racing accident.
The man has been named as Denis Welch.
"It is with great regret that the organisers of the Silverstone Classic have to report that, following an accident in a race for HGPCA pre-66 Grand Prix Cars today, Sunday 27th July, the driver of car number 19, Denis Welch, succumbed to his injuries later in the circuit’s Medical Centre."
Two former RAF fighter jets have been sold at auction at the Silverstone racetrack in Northamptonshire for a total of more than £140,000.
The 1976 Hawker Siddeley Harrier GR3 and 1988 Panavia Tornado F3 went under the hammer without a reserve.
The Harrier was bought by a private buyer in Essex for £105,800 and the Tornado went to a woman from the UK for £36,800.
The planes were lots in The Silverstone Classic Sale.
Two former RAF fighter jets are to be sold at a public auction at Silverstone racetrack in Northamptonshire today.
A 1976 Hawker Siddeley Harrier GR3 Jump Jet and a 1988 Panavia Tornado F3 will go under the hammer.
The Harrier, which served during the Cold War, Belize and the Falklands, is described as being preserved "in almost time capsule condition".
We've never offered anything like this before and it's a privilege to be able to offer one of, it not the finest, Harrier in the world.
The history and provenance of the plane, combined with the fact that the aircraft is so complete, means this really is an exciting opportunity.