The equipment is able to detect chemical weapons and is being brought in to search for anthrax.

The event, which takes place in March at the Cheltenham Racecourse, will be visited by the Queen for the first time in 50 years.

Although there has been no specific threat from terrorist organisations, racecourse directors say it makes sense for them to take precautions.

'Royal family'

Edward Gillespie, managing director of Cheltenham Racecourse, said: "We are trying to re-assure people that we are taking ultimate care, if the equipment is there, then we should have it to hand.

"Security has always been at the absolute top of our agenda in terms of reassuring people that they are in good hands.

"We have experience over many years of members of the royal family attending," he added.

Fifty thousand people a day go to the racecourse during the festival.