The phenomenon of "floating storage", which has been brought about by a huge over-supply of global tanker capacity and unusual market conditions, is just one example of the multitude of ways in which a small group of private, mostly Swiss-based companies have become adept at turning vast profits from the closed and often murky world of independent oil trading.
The resulting profit can be anything between 15 and 20 per cent – tens of millions of dollars – even after the cost of hiring a tanker is deducted.