The business is challenged. Investment bank chief executives plan to constrain it or optimise it. Difficult conversations are being had. Say it how you will, prime brokerage is being upended.

The world's largest investment banks are facing difficult decisions about how much resources they dedicate to the hedge fund industry - which has $3.1 trillion in assets under management - under new global banking rules that impose leverage, liquidity and capital constraints. Some hedge funds, particularly smaller operators and those that rely on high levels of leverage in their investment strategies, are being hit.