When Josh Barrickman became known as the new “bond king”, his colleagues teased the taciturn fund manager by leaving paper crowns from Burger King at his desk.

The low-key Ohio native may not have the high profile of bond market stars such as Bill Gross but he has earned his title. The fund he runs, the Vanguard Total Bond Market, is the world’s biggest fixed income fund, with $247bn in assets under management.

The fund’s table-topping position exemplifies the revolution under way in the $9tn  US bond market. Unlike the freewheeling, actively-managed Total Return fund once run by Mr Gross, Vanguard’s flagship bond fund is a passive, index-tracking fund. It takes a smaller fee from investors and tries to track the market, not beat it.