It was in the late 1980s that Ken Griffin set his sights on what Citadel Securities would eventually become. An early trade with Susquehanna Investment Group paid out less than the young Griffin was expecting. One version of the story has him sitting on the telephone in his Harvard dorm room, complaining to the Susquehanna trader and vowing to start a competing business to change the entire market, according to former employees and acquaintances.

Whether apocryphal, few would dispute that Griffin — the founder of Citadel Securities and its related $35bn hedge fund Citadel — has fulfilled this vow.

The initial ideas that would evolve into Citadel Securities took life in the early 2000s on a separate floor of the hedge fund’s old Chicago headquarters. Since then it has grown into one of the largest trading houses in the world, involved in roughly one in four of all US stock trades and nearly 40 per cent of all those involving individual retail investors.