This chart struck me as being very counter-intuitive.
With the growth of world trade, it might be reasonable to think that UK would become more dependent on food produced overseas. In fact, since 1970 the proportion of domestically produced food has actually increased.
Food self-sufficicency peaked in 1991 when three quarters of food demand was produced by domestic farms. Self-sufficiency has fallen since then, but it still remains over 60 percent, which is surprising for a country with such a high population density.
Why did UK self-sufficiency increase so quickly and then decline. Has anyone ever met a farmer who didn't think food production should be subsidized? During the 1980s, the EU's common agricultural policy was extremely generous to any farmer who over produced. More recently, the scheme has become less generous. Farmers have responded by cutting back production.
It is always about incentives.