As US president-elect Donald Trump prepares to re-enter the White House, global trade has become a contentious issue.

Mr Trump has threatened to impose tariffs – that is taxes at the border – on all goods imported from a host of nations, including neighbours Canada and Mexico as well as economic rival China. That risks igniting another trade war, with companies and consumers around the world affected.

Has global commerce always been so contentious? Rob Young looks at some of the key developments in international trade throughout history to work out how we got to the system and practices we have today.

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(Picture: Hands of woman showing seeds in a souk. Seeds are believed to be one of the earliest items to be traded in the world. Credit: Getty Images)