Michael Spencer oversaw some big deals in building Icap into a £3 billion brokerage sitting at the heart of over-the-counter derivatives markets. But his toughest challenge could be making a success of Nex Group, which is what remains of his company following the sale of its trademark voice-broking activities to rival Tullett Prebon.

The deal, completed December 30, leaves Nex as a slimmed-down business focused on electronic trading, post-trade and financial technology.