It is a mid-sized Belgian business that oils the wheels of global finance from a tranquil lakeside south-east of Brussels, across the road from a 19th-century château. But the peaceful existence of the Society for Worldwide Interbank Financial Telecommunication — better known as Swift — has been ruptured by a transatlantic battle over the Iran nuclear deal. President Donald Trump’s reimposition of nuclear sanctions on Tehran poses a direct challenge to the business model of Swift, a company that bills itself as an internationally available, politically neutral “utility”. As the EU prepares measures to respond to the US move, Swift provides an acute example of how companies risk being caught in a transatlantic squeeze, and how the dispute might trigger wider fallout for international business. Mr Trump reactivated the US sanctions against Iran last month when he pulled Washington out of the landmark 2015 nuclear accord with Tehran. Unless Swift wins an exemption, it will be required by the US to cut off targeted Iranian banks from its network by early November or face possible countermeasures against both its board members and the financial institutions that employ them.