understanding food supply and all the ins and outs of it is not within most people's grasp or interest!
The UK has not been self-sufficient in food for the last 200 years. The industrial revolution meant that workers could earn more by moving to the towns and working in factories, so agriculture began to be less important. At the same time, the British colonies were geared up to provide the mother country with food - wheat from Canada, lamb from New Zealand, fruit from Africa etc.
The big problem with this was emphasised during WW2, when the food could not get through. Despite almost every square inch of land being turned over to agriculture, including public parks, rationing had to be imposed to ensure than everyone received the bare minimum to eat. One egg per person per week, a jar of jam every two months, 2oz of butter, 2oz of tea a week, meat to the equivalent of two lamb chops a week etc. What looks today like the daily consumption for an adult had to last a whole week.
Over the last 70 years, the UK economy has become ever more integrated with that of the rest of the world, but most notably with Europe - which is of course only 22 miles away. Modern logistics mean that supermarkets only have space to stock 1-2 days worth of fresh food (as it can be replenished daily if necessary), 3-4 days of semi-fresh goods (e.g. a delivery of 50 cases of frozen pizzas twice a week) and about 10 days worth of other foods (pasta, rice etc). Under normal conditions, a typical supermarket has sufficient stock to serve its customers for about 5 days before running out.
When people buy additional food - e.g. at Christmas and New Year - the supermarkets struggle to keep everyone supplied despite ordering extra stocks, so fresh products in particular run out far quicker. As this is foreseeable, new stock is already on the way to the shops in time for the first opening day - e.g. after Christmas.
The problem with even a 'soft' Brexit is that this supply chain will be disrupted, so that various goods will be in short supply or even become unavailable. If a truck-load of Spanish fruit or French yoghurts is delayed for 5 days, the goods risk going off before they can be delivered. The result is that the shops will have less stock - and if shoppers then panic-buy (having spotted the empty shelves) the supermarkets will empty in a matter of hours - just as they do at Christmas.
A hard Brexit would create huge problems. The hauliers predict that as little as 20% of lorries will be able to cross the Channel. Instead of 10,000 lorries a day, only 2,000 might get through. If a third of these lorries are carrying food, or food ingredients, or packaging materials, then instead of over 3,000 lorries getting through, only 600 might get through.
Food would then have to be rationed by:
- The supermarkets limiting the amount that people can purchase (good luck to the cashiers and security guys when they try to enforce this);
- Goods become rationed by price - as the demand increases, prices go up and only those who can afford to buy can do so;
- Formal rationing - as in WW2 - which requires a Census to determine who is eligible for food rations, and a huge system in order to produce, distribute and administer the rationing system of ration books, stamps, smart cards etc. and which would be impossible to implement by 30th March.