Tullett Prebon Plc has completed the 1.28-billion-pound purchase of the voice-broker business of its former rival ICAP Plc, creating a dominant firm in the business of matching trades between banks. The new business, which has been rebranded as TP ICAP Plc, has 3,425 brokers who will continue to run competing desks, trading under the Tullett Prebon and ICAP brands.