Turquoise, one of a new breed of alternative trading systems that potentially threatens the future of Europe's exchanges, registered record trading volumes last week as it prepares itself for a sale by the end of the year. The development promoted claims by analysts that the system's bank owners could be trading heavy volumes to increase the value of a sale.

The London-based system performed a record 11.05% of FTSE 100 trades on August 11, 7% of Dax trades on August 12 and 8.06% of Cac40 trades on August 13, according to a spokeswoman. It also hit a high in Dutch stocks on Monday, and its dark pool traded a record €56.8m ($80.8m) on August 13, she said.