Eagle eyes....this is bad customer service anyway you look at it. In this opinion article, BloombergView looks at the intricacies of Barclay's "last-look function" within its FX electronic trading business that has landed the investment bank a $150m fine. Once you read the quote from Barclays Managing Director and Head of Automated Electronic FX Trading, it will be quite apparent why it landed them in such trouble.
On June 6, 2011, in an email discussion about Last Look, a Barclays Managing Director and Head of Automated Electronic FX Trading wrote: “Do not involve Sales in anyway [sic] whatsoever. In fact avoid mentioning the existence of the whole BATS Last Look functionality. If you get enquiries just obfuscate and stonewall.” It comes from this New York Department of Financial Services consent order with Barclays, which agreed to pay a $150 million fine over the "last look" function in its electronic foreign-exchange trading business.
http://www.bloombergview.com/articles/2015-11-18/barclays-took-a-last-look-at-its-fx-trades