The US is a major trade and investment partner for the UK - by some measures the biggest of all.
One issue on President Trump's agenda while he is in Britain will be whether - and how - to deepen that relationship.
So just how intertwined are the two economies?
As a single country the US is the largest export market for the UK. It is, however, well behind the EU when the bloc is viewed as a single market.
There is some logic to viewing the EU in that way, as it has a single external trade policy and most of its members share the same currency.
As a supplier of goods and services to the UK, the US comes in second, behind Germany.
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