As with Chinese Olympic swimmers, so it is with investment banks: when someone blows the competition out of the water, rivals immediately start asking whether there is something fishy going on.

Few investment banks have navigated the post-crisis fallout as well as JP Morgan, which has hoovered up market share at the expense of shell-shocked rivals. In the past year in particular it has taunted rivals by adding first-class profitability to its dictum of doing first-class business in a first-class way.