When Mr Stephen Olson began his career as a US trade negotiator in the 1980s, the subject of trade was an arcane one.

It was the domain of number-crunchers, concerned with lowering sky-high tariff levels post-World War II, on such obscure items as industrial pumps. This was boring stuff, said Mr Olson, joking that speaking about his work at dinner parties was a surefire way to bring gatherings to a close.