The waters have partly settled over the White House’s one-sided war of words between a man who dodged the draft to serve his country and a war hero.

Trump at one point accused the Ukranian president of risking World War Three by standing up to Russia. That is hopefully an exaggeration but when it comes to trade Trump has started a world war over tariffs.

He is ignoring the rules that govern world trade knowing the consequences will be bad for growth, stability, and the finances of the voters that put him in power. Prices will rise in the US and stock markets have dropped this week in response to the business chaos that lies ahead.

Tariffs cannot deliver economic growth – in fact, they deliver the opposite. Canada, America’s biggest trading partner, has already hit back and will do so again if the US tariffs continue. Mexico will announce its retaliation this weekend and China has already responded with tariffs targeted to hurt Trump’s political base.

Agriculture has been dragged into this war from the outset. China has targeted US farm products including grain, protein crops, beef, pork and dairy with tariffs that will make them uncompetitive. This is a big blow to US farmers who are enthusiastic Trump supporters. They may hope now there are gaps to fill on shelves at home, but one of Trump’s Achilles heels is that he promised to reduce the price of food on supermarket shelves.

He has failed to do so. Prices are continuing to rise and he is being taunted daily over his failure to deliver lower food prices.

There is an irony in this for American farmers. Agriculture normally does well when political conditions are difficult and food security becomes more important. But the misuse of tariffs changes that game. Others will be lining up, led by the EU, Australia and New Zealand, to target the opportunities Trump’s tariffs have created in China. It is a top market for food with a prosperous middle class driving demand for premium products.

This is a great opportunity for the EU and UK to target gaps in a prime market. We could gain in the short term from the losses American farmers face. But tariffs, like nuclear war, are a zero-sum game with no long-term winners. It is why there are World Trade Organisation rules.

The rules that govern international trade and have successfully settled disputes for decades are being smashed by the country that was instrumental in establishing those rules – akin to what Trump is doing with Nato. Europe is next in Trump’s tariff targets. He is convinced the EU is out to undermine the US, but in reality it has, over the years, squandered a balance of trade surplus with Europe into a deficit.

This is not down to unfairness in Europe, but reflects America becoming less competitive globally. Protein imports are a prime example, where Brazil and not the US is now the main supplier to Europe.

Trump believes hitting Europe will play well with his supporters. This would be a blow to European food and drink. Its big three export markets are the UK, China, and the US. It is very much open to question if Brexit, which Trump loves, will allow the UK to escape tariffs.

That looks unlikely as Trump may seek in return further isolation from the UK’s biggest export market which is the EU. The EU already, like China, has a

hit list drawn up to respond to US tariffs and those are designed to hit hard and where they will hurt. Tariffs do not create winners, only losers. The EU will be taking on what remains the world’s biggest economy. Trump supporters in industry and his voters are already seeing business values fall and they will soon feel the impact of rising inflation. World trade is now a game where the referee has left the pitch.

The UK is doing well diplomatically between the US, Europe and Ukraine but when it comes to trade, scale makes it a weak player in the tariffs game. It cannot avoid being a victim. It is shoring up defence spending and looking at even deeper spending cuts to pay for worsening economic growth. Now should be the time to embrace agriculture and give food security a new, central strategic priority, as the EU is doing.

However, the need for that penny to drop has yet to reach Westminster.