The fear that has held up the commercialisation of GM crops in Britain for four years is not connected with eating GM produce, but about the potential effect on wildlife of the extra-powerful herbicides used to control the crops.
All four GM crops currently intended for planting in Britain have been genetically engineered to tolerate these chemicals - of which Monsanto's Roundup and Bayer's Liberty are the best-known. They are "broad-spectrum" herbicides, which means they are so deadly they kill every plant they encounter. Their previous use was to clear fields entirely - they could not be used in the growing season, as they would kill the crop itself.
But with the advent of GM crops that can take these weedkillers, they can be used throughout the year. The fear of English Nature, the Government's wildlife advisory body, is that the insect, plant and bird life that has been enormously damaged by four decades of intensive farming, in which chemical weedkillers and pesticides have played a leading role, will be damaged even further.
With GM herbicide-tolerant crops, they fear, there will be nothing left at all in the farmer's fields but the crop. They call it "green concrete".
In 1999, English Nature persuaded the Government to carry out a four-year programme of trials to see if the GM crops and their weedkillers really did make things worse for wildlife. The GM companies agreed to a planting moratorium while this was done.
The farm-scale trials were carried out at 263 sites using four crops (fodder maize, beet, and winter- and spring-sown oilseed rape). They matched the weedkiller regime of the GM crops against that of conventional crops, and compared the effect on plants, insects, snails and other small lifeforms, of both.
Some anti-GM campaign groups protested against the trials themselves, saying they risked the escape of GM genes into the environment. A number of attacks on trial sites were made by activists, the most celebrated being that by Lord Melchett, then executive director of Greenpeace, and 27 other members, on a Norfolk farm in July 1999. The protesters were arrested and charged with criminal damage, but were later acquitted by a jury at Norwich Crown Court.
The trials will finish in July when the last crop of winter-sown oilseed rape is harvested. The results will then be analysed, peer-reviewed and published by the Royal Society.
If they show real increased harm to the environment, the Government could halt the commercialisation of GM crops in Britain, despite the fact that one crop has already been authorised for release by the EU, and the other three are close to being authorised.
GM products and protests from the Double Helix to th Flavr Savr tomato
By Michael McCarthy and Joanne Sokill
1953: The double-helix form of the DNA molecule, the basis of all life, is unravelled by James Watson and Francis Crick, making biotechnology a possibility.
1973: Scientists successfully transfer DNA from one organism to another for the first time, making it "recombinant" (viral DNA is added to a bacterium).
1983: Kary Mullis, Californian scientist and surfer, discovers the polymerase chain reaction, which allows tiny pieces of DNA to be replicated rapidly and thus permits large-scale genetic engineering. Mullis wins the Nobel prize for Chemistry.
1983: US patents awarded to companies producing genetically engineered plants. The US Environment Protection Agency approves the release of the first GM crop, virus-resistant tobacco.
1987: The first deliberate release into the environment of a GM plant in Britain - a potato.
1990: The US stages first trial of a GM herbicide-tolerant plant - cotton.
1994: First GM food, the Flavr Savr tomato, inset, is approved by the US Food and Drug Administration.
1996: First GM soya grown in the US.
1997: People realise Monsanto GM soya is being used, unlabelled, in processed foods in the UK and protests begin.
June 1998: Prince of Wales says he would neither eat GM produce nor serve it to his family and friends.
July 1998: English Nature, the Government's wildlife advisory body, calls for a moratorium on planting of GM crops while trials are carried out on the effects on wildlife of their associated weedkillers.
August 1998: 'World in Action' TV programme reveals that Dr Arpad Pusztai, a scientist at the Rowett Research Institute in Aberdeen, claims to have found that GM potatoes carrying an insecticide gene caused health damage in rats. Major food scare ensues: Dr Pusztai subsequently sacked after allegations that his research was flawed.
October 1998: Prince of Wales suggests consumers should boycott GM crops.
February 1999: The Environment minister, Michael Meacher, persuades GM companies to agree to a planting moratorium while farm-scale weedkiller trials of GM crops are carried out.
Spring 1999: Pilot phase begins of farm-scale trials.
July 1999: Lord Melchett and 27 other Greenpeace activists attack Norfolk farm engaged in the trials and trash the crop of GM maize, the most prominent of several such attacks.
Spring 2000: Farm-scale trials of GM crops begin in earnest across Britain.
September 2000: Jury at Norwich Crown Court acquits Lord Melchett and other Greenpeace activists of criminal damage.
September 2001: Government's main GM advisory body calls for public debate on whether to permit commercial growing.
Spring 2003: Farm-scale trials coming to a close.
June 2003: Nationwide GM debate begins.
September 2003: Possible results of farm-scale trials.
Autumn 2003: Government decides on GM crop commercialisation in the UK.Reuse content