The town of Malvern is a 45-minute drive north-west of Philadelphia. It has a population of 3,400 or so, and was the site of a minor drubbing for George Washington’s continental army in 1777. It is, in many ways, a fairly unremarkable, affluent corner of the American north-east. But Malvern stands out in one way: it is home to $10trn in assets under management.