This all came out some years ago; this is just a followup lawsuit from the people who opted out of the first round of litigation. In short: It didn't work ver

This all came out some years ago; this is just a followup lawsuit from the people who opted out of the first round of litigation. In short: It didn't work very well, but that's not the point. Longer form: Traders from several banks shared client positions, and made very enthusiastic if somewhat amateurish efforts to manipulate the price at the close. The core of it was trying to figure out if there was going to be a lot of pressure one way or another on various price pairs, and then trying to manipulate the spot price at the close to take advantage of it. For example, if you know a few large clients will be selling a net of £100m for USD, you might try accumulating a bunch of USD slowly in advance of the close (to avoid driving the price up), so when the sales hit you can profit. Or you might try and buy a little USD early, then hold off until right before the close, and buy a bunch very quickly to try and spike the price heavily, making your earlier purchases more valuable. Etc. None of it sounded especially like it would work, many of their techniques were completely contradictory, and nobody really bothered to try and calculate if it did work. The FCA said "that it is not practicable to quantify the financial benefit". One example of a very good trade apparently made US$100k for the offending banks (on a volume of over $500m); many others lost money. Total profits from the activity were at most a few millions of dollars per bank per year, if they even came out ahead; their fines were orders of magnitude higher. Or as the CTFC described it: > If traders in the chat room had net orders in the same direction as what they desired rate movement at the fix to be, then the traders would at times either (1) match off these orders with traders outside of the chat room in an attempt to reduce the volume of orders in the opposite direction transacted during the fix period; (2) transfer their orders to a single trader within the chat room who could then execute a single order during the fix period; or (3) transact with traders outside of the chat room to increase the volume traded by chat room members during the fix window in the direction favored by the private chat room traders In other words, to try and drive the price of GBP up the traders might 1) try and buy GBP from outside banks to stop those banks from selling GBP at the close 2) not do anything in particular 3) try and sell GBP to outside banks so that the traders wouldn't need to sell GBP at the close. It seems pretty unlikely that these are all valid strategies, and indeed, they mostly didn't seem to work. > In what sense were these individuals 'manipulating' these markets? Primarily in the sense they had intent. The actual impact seems questionable. But with chat transcripts that damning, what more do you need? (Matt Levine has written about this extensively, among other places, here: https://www.bloomberg.com/opinion/articles/2014-11-12/banks-manipulated-foreign-exchange-in-ways-you-can-t-teach https://www.bloomberg.com/opinion/articles/2014-11-12/banks-...)