When Turquoise, the equities trading platform, on Monday said it had received UK regulatory approval for a new service that aggregates large orders and routes them to other trading venues, it did more than highlight the proliferation of “dark pools” in Europe. It pointed to an emerging trend: dark pool operators are starting to act like brokers.

Since competition in equities trading was unleashed 18 months ago by the European Commission’s Mifid directive, share trading liquidity has fragmented not only between exchanges and the new trading platforms but also between a crop of dark pools, many operated by bank brokerage arms. That has made it hard for traders to know where their large orders can be matched most efficiently.