The experience of the 1930s was similarly instructive. Faced with the stock market crash and the Great Depression country after country decided that the best way to deal with the domestic problems was to raise tariff barriers. For a few short weeks after they went up the impact was positive. Then other countries raised their own barriers and no one gained anything. In fact the wars over tariff controls acted as a nasty drag on the world economy, made the Great Depression worse and contributed to the economic misery which resulted in fascism and the Second World War.
So one of the very few things that virtually every economist agrees on is that other things being equal free trade is helpful. The law of comparative advantage is pretty clear and simple. Countries will be better off if they focus on doing and selling abroad the things that they are best at doing and then engage in free trade to buy the things that they are less good at selling.
It is therefore being taken as self evidence at the moment that the UK will be fine after exit provided that it can get access to free trade deals with the EU and other major nations. Unfortunately in reality it isn't that simple. The kind of trade deals you get matter and the position your country is in when it enters into the deal matters even more.
A country that is efficient at providing goods and services that people want to buy always does well out of free trade. A country that is inefficient tends to find the experience a lot less pleasant. A failure to succeed in competitive markets is one of the key reasons why India declined into poverty and colonial occupation. It is the prime reason that China became so weak that it went from being the richest and most advanced country in the world to one of the poorest and worst organised.
Complete free trade results in the country with the cheapest, best designed or most technologically advanced products and services selling a lot abroad and becoming steadily richer whilst those without that stand still or go backward. The experience of the UK since the 1970s has been of serious decline in traditional industries in the face of competition from factories in other countries where wages are very low. It has never quite made up for that by the "success" of its financial service industries. Now that the reputation of UK financial companies for honest reliable trading has been shot to pieces it is far from clear that the country is going to be strong enough to compete successfully in enough areas. Removal of trade barriers with countries like China opens our industry up to fierce international competition. We are not guaranteed to win that competition.
Currently the UK has the largest balance of payments deficit it has ever had. If Brexit is to take us to those sunny uplands then something has to be done to make what we sell more attractive. In industry this means investment. In culture, science and medicine - all of which are good exporters for the UK - it means investment in education and a free and tolerant environment. In finance - overwhelmingly our biggest earner - it means re-establishing a reputation for honesty and reliability which has been shot to pieces by scandal after scandal and the 2008 collapse of badly controlled financial markets. In technology it means investing to get at the forefront of the next phase of low energy and renewable energy products and ways of working.
In short we need a strategy for success that invests and guides the economy to make it more competitive. Unfortunately virtually all of those involved in negotiating Brexit and agreeing the terms of our new trade relationships with the rest of the world aren't mentally equipped to achieve this. They have been ideologically brought up in a school of thinking that says the only solution to an economic problem is to remove all barriers to uncontrolled economic forces and to let the competitive market sort out what happens. Virtually the only trade negotiators with any experience that we have in the UK are ones that have worked on the Trans Atlantic Trade and Investment Partnership. TTIP works on a simple principle that national governments shouldn't be allowed to get in the way of free trade. Instead lawyers hired by multinational corporations are empowered to take national governments to court to force them to accept what the market dictates. This means that a tobacco company can sue a government for insisting that it sells its products in plain packages carrying health warnings. Incredibly this has actually happened. That is not my idea of an attractive and well planned free trade deal.
What we need is not unfettered free trade that allows monopoly corporations and their powerful lawyers to bully elected governments. What we need is managed trade guided and, where necessary and helpful, directed by national and international government.
Two things are therefore vital for the success of Brexit. One is that the UK develops and implements a clear and effective economic strategy that helps our country compete successfully in the world. The second is that we strike free trade deals that are controlled by international governmental bodies that properly represent the electorate of all the countries involved. Not by corporate lawyers.
As it happens these are also exactly what we need to achieve if we remain in the EU when the electors have the chance to see the actual deal on offer as opposed to project overblown promises. It is possible that Theresa May's government will use the power of the UK state, adopt a plan for the UK and its regions and start the long process of recovery of UK competitiveness. It is also possible that it will find and hire trade negotiators who will be strong and determined enough to stand up to the lobbying of powerful multi-national companies who want to see the UK government powerless to resist whatever market forces dictate. But that would involve them dumping 40 years of ideological conviction that the market always and everywhere has the solution to every single economic problem. So be very careful when May's government announces that it has just negotiated a wonderful new free trade deal. Free trade deals aren't always an unadulterated blessing.