By the middle of May 1940 Nazi Germany controlled the west European coastline from Narvik to Bayonne, and U-boat attacks impacted severely on British food imports, such that the London docks saw only 25 per cent of their normal traffic. Countries previously supplying such food items as butter, eggs and bacon, as well as timber, were now under German occupation. It is remarkable that 99 per cent of all ships sailing from North America to Britain during the war arrived safely. But much of that shipping was desperately required for munitions rather than food. Furthermore the infrastructure at British ports and on the railways, poor labour relations between dockers and their employers, together with Luftwaffe air raids on the docks, meant that the overall import system was under severe strain.

Following the disastrous Norwegian campaign Chamberlain resigned as Prime Minister on 10 May 1940, to be replaced by the bellicose Churchill, whose new cabinet was immediately apprised of the need for national food security. To the surprise of many, R. S. Hudson was appointed Minister of Agriculture and Fisheries with Tom Williams as his Joint Parliamentary Secretary. On his first day in office the latter declared his particular interest in the CWAECs and the links between them and Whitehall. Meanwhile scientists, such as the nutritionist Sir John Boyd Orr, were determining the main requirements for food production under siege. The wartime system of rationing (in 1940, meat and bacon at first, followed by sugar, tea, butter and margarine) and food control (the Ministry of Food became the sole buyer of all rationed foods) was in general a great success: ‘the Kitchen Front was the only one where Great Britain never lost a battle.’

As a general principle, the aim was to produce, in order of importance: milk, bread corn (initially wheat, but later also rye and barley), potatoes, sugar beet and animal feedingstuffs. Of course, not all farms were equipped to gear their operations in this way, and local flexibility had to be retained.