"Electronic oil casino." That is how David Hufton, the head of PVM Oil Associates, has defined some of the electronic exchanges on which Brent and West Texas Intermediate, the world's oil benchmark, trade.

That casino has proven costly to the company after a broker, identified by traders as PVM employee Steve Perkins, engaged in what PVM said was "unauthorised trading" in the early hours of Tuesday, buying "substantial volumes of futures".