Alex James: It doesn't take a fertile imagination.. I'm told there is only one fertiliser supplier for the whole of the UK and I wouldn't be at all surprised - I think it's pretty much the same story with pig food. Even if it's true and our food supply relies on a commodity controlled by a Russian monopoly, that would still not be the scariest thing about fertiliser. The really worrying thing about fertiliser is how easy it is to turn it into an explosive device. I didn't realise quite how easy. All that is required is a detonator. A firework would probably do it. The bombs in Oslo, Oklahoma and Delhi were all made from ammonium nitrate, common agricultural fertiliser, and in the run up to the Olympics, Britain's farmers are being warned to keep their supplies - often running to tonnes of the stuff - safe. As it's a commodity with a fluctuating price, farmers tend to buy it when it's cheap and store it until they need it. Recommended precautions such as ensuring any stored outside is "fully sheeted" don't sound very reassuring, but what else can be done when so much of what we eat depends upon the stuff? It's thought terrorists might take small amounts from several farms to avoid detection and the National Counter Terrorism Security Office recommends that stock checks are carried out regularly and any amount that goes missing is reported immediately. But all anyone needs to do to buy as much ammonium nitrate as they want is to get a farm-holding number which, if my dear friend Bob can get one, is clearly not beyond the wit of anyone at all. In reality you can probably get away without a farm-holding number. I don't use the stuff - our farm is organic - but one place I spoke to said all I would need to do would be to set up an account and place a minimum order of three tonnes. I don't know which is scarier - bombs, or that we need Russian dynamite to make a bowl of breakfast cereal.