To trade freely with the EU after leaving the single market and customs union, we will need to negotiate a trade deal. If we can’t, then the UK economy will be in big trouble.

This familiar line of thought is wrong. Free trade does not require trade deals between governments. People living in Leeds can now trade freely with people living in Bristol. Yet there is no trade deal between the Leeds City Council and Bristol City Council. Suppose councillors decided to take an interest in trade between the two cities and struck a deal. The terms of the deal could only create barriers to trade where there were none.

The same goes for international trade. If governments genuinely sought free trade, there would be nothing to negotiate. Each would simply refrain from creating any barriers to trade. This is precisely what the UK should when it leaves the customs union in March 2018.

As Professor Kevin Dowd argues in a paper published today by the Institute of Economic Affairs, the UK should adopt a policy of unilateral free trade. We should simply eliminate all tariffs on imports, regardless of what tariffs foreign countries impose on their imports from the U.K.

This will strike many as a crazy policy – all give and no get. But that is because they do not understand how free trade benefits a nation. The principle gain comes from cheap imports.