Re-hypothecation: an ugly word with ugly consequences. Like many other providers of broking services to hedge funds, the European arm of Lehman Brothers was fond of using collateral posted by its clients as collateral for activities of its own. The practice seemed harmless until the broker went bust, leaving hundreds of funds facing a long struggle to claw back assets.

That shook the prime brokerage industry, as funds scrambled to unwind trades with the riskiest counterparties. A year on, the threat of implosion of another prime broker has receded. But the landscape has been redrawn.

The most notable change is diversification. Pre-Lehman, multibillion-dollar funds would treat a single prime broker like a personal butler, able to serve up swaps or stock loans at a moment's notice. Now, investors expect even medium-sized funds to have three at a minimum – ideally one in the US, one in Europe and one in Asia, to spread bankruptcy risk.