A decade ago, trading foreign exchange benchmarks was in many ways a human affair. A buy-side client would call up a dealer bank with an order, a trader would assume the risk and try to transact as carefully as possible without tipping their hand to the rest of the market.

Since then the role humans play in trading benchmark fixes has rapidly diminished. In their place are sophisticated computer programs that are more patient and stealthier when working these orders into the market. This has