"Understandably, supermarkets have worked out the cost of applying these new tariffs in this British Retail Consortium exercise on their own supply chain data - the total is £3.1bn next year, versus zero this year. That is worth about £112 per household."
So about £2 per household per week.
That's only the effect of the tariffs on food prices. There are also non-tariff costs to consider.
If there are shortages of food items, e.g. if fewer goods cross the Channel, then the market responds by increasing prices - the market is an auction where the highest bidders can buy what is available and those who cannot pay miss out.
The figure does not include the additional costs caused by the increased red-tape that importers will face - and pay for people and IT systems to complete, adding to their costs - or the increased costs of freight as lorries are stuck in queues and not earning money.
The figure does not include the increased cost of warehousing as supermarkets, retailers and wholesalers are forced to hold buffer stocks. JIT supply chains have few warehouses - the lorries on the road are effectively rolling warehouses.
The figure does not consider the costs incurred if food production lines need to shut down. A frozen pizza uses mushrooms and onions from Holland, cheese from Ireland, tomato paste and olives from Italy, meat from Denmark, and is packaged in a box made from cardboard that comes from Sweden. If any one of these items is delayed, the production line stops.