Flour is obtained by milling - grinding grain to separate the inner kernel from the outer husks. For thousands of years, people milled their own flour by hand using a stone or a pestle and mortar. Improvements to the stones used for milling meant better flour, but milling was still done on a very small scale.
From the Middle Ages onwards, more sophisticated forms of milling were used. These harnessed the power of water or wind to turn the millstones. Before the 19th century, wooden windmills were very common throughout Europe.
Dozens of windmills stood in what is now London, though almost all have long gone.
A view of Blackheath, by John Charnock. © NMM