From the BBC:
Will food be more expensive after 1 January?
Under WTO rules, supermarkets and other importers would have to pay substantial tariffs on many foods they bring in from the EU. Meat and dairy products face particularly high tariffs, but many other areas including fruit and vegetables would be also affected.
The BBC can't even be bothered to read its own summary of what the WTO is about:
The WTO was established in 1995, when it took over essentially the same functions from the General Agreement on Tariffs and Trade (Gatt), which came into force in 1948.
One of the motivations for creating the Gatt was a wish to dismantle the barriers to trade that had been erected between the two world wars. Most economists regard the establishment of these interwar trade barriers as misguided and say they probably aggravated the Great Depression of the 1930s...
A series of eight "rounds" of negotiations under the Gatt led to the progressive reduction in trade tariffs - taxes which are imposed only on imported products.
The minimum - and indeed the recommended - tariff imposed under WTO "rules" is precisely zero. Given how useless the UK government is, they might well impose tariffs on imported food, but this will be entirely self-inflicted. This will be the UK government waging economic warfare against its own people, and if the EU imposes tariffs on imports from businesses in the UK, that is them waging economic warfare against citizens of EU Member States.