Nearly five years ago, Morgan Stanley went on a hedge fund buying spree, snapping up stakes in three hedge fund firms in as many days. A global financial crisis later and opinion remains divided as to whether buying all or part of a hedge fund manager is a good idea.

The Volcker Rule, which has effectively banned investment banks from using their own money to speculate in the markets, has raised the question of whether banks that bought stakes in hedge funds are going to have to sell them.