Currency dealing used to be simple. “It was always exactly the same,” recalls one fund manager. “You’d ring up your phone broker – in London they were always called Sid or Joe; in New York, it was Vinnie – you’d tell them what you wanted and between half an hour and an hour later, they’d come back with a price.”

However, with the birth of new multi-dealer e-platforms in the early Noughties, foreign exchange became a fast and competitive market in which anyone could make markets. This allowed high-frequency trading firms to set prices quicker than banks, offering buyers in the client-to-dealer or even the interdealer market tighter bid/ask spreads than the banks could offer. HFT strategies depend on the kind of fast, accurate pricing that only comes with electronic trading.