Nicotine is colourless. In theory, cigarettes can be made out of potato or tomato leaves. Some programmes designed to help people stop smoking also advise giving up potatoes and tomatoes in order to eliminate low-⁠level nicotine intake completely. In small doses, the nicotine compound that is present in all these plants produces feelings of pleasure. That’s why tobacco is more addictive than either cocaine or heroin. But it’s also why we sometimes find ourselves craving chips or pizza.

In large doses, however, nicotine is as deadly as the nightshade whose relative it is. The nicotine in a single cigarette, if taken direct into the bloodstream, would be fatal. Eating one cigarette could make you severely ill. Swallowing a packet of ten would definitely kill you. In 1976, the Department of Health urged pregnant mothers to wear rubber gloves when peeling potatoes. More than a kilogram of potatoes eaten at a single sitting would be certain death.