The conversation turned to how Reuters plan to support Mifid's requirement for post-trade transparency. He described how, today, Reuters provide information on prices by using a concatenation of an equity's symbol (e.g. "VOD" for Vodafone) and the trading venue at which the trade was made (eg. "L" for London"). Hence: VOD.L.
He explained that, when trades from other venues (e.g. those internalised by large institutions or on other trading facilities) are published, he anticipates that Reuters will make those streams available by assigning new suffices to each of the venues. (Implicit in the conversation was that they already do that for some of the existing exchanges)
He then made a very interesting point: Reuters also provide an aggregated feed, with the "X" suffix: So "VOD.X" carries information on trades from all venues that Reuters receive feeds from.
This interested me because, when I want to check the price of William Morrison stock, I use the MRW.L symbol in Yahoo Finance. Perhaps this means I'm not seeing a full picture?
I just tried MRW.X on Yahoo, to see if I could get figures that included all other venues where Morrison shares trade. Yahoo didn't want to play ball.
Oh well.... maybe I should try again on November 1.