The UK government has sanctioned a secret trial of genetically modified (GM) wheat, which will be grown on a three-acre site in Hertfordshire next year.

The site, at the Rothamsted Research farm in Harpenden, will be protected by a high fence, and the police may also guard the area. Previous attempts to grow GM crops at the site have been attacked by protestors.

The trial will involve crops that have been adapted with a chemical to deter aphids and attract predators of the pest.

Two other GM trials will be run at the same time. The University of Leeds will be testing pest-resistant potatoes and the Sainsbury Laboratory at the John Innes centre in Norwich is to run trials with blight-resistant potatoes.

Despite the involvement of the supermarket, the Department for Environment, Food and Rural Affairs (Defra) says that none of the test crops wil enter into the food chain. A Defra spokesman has said: "Protecting consumers and the environment is our top priority and we're permitting a tightly-controlled, small-scale trial, in which none of the wheat will enter the food chain."