The London Stock Exchange is for the first time set to allow traders to place “hidden orders” on the exchange in a move likely to fuel controversy over “dark pools” and market transparency.

Hidden orders are large orders – for example of 20,000 shares in a particular stock – placed on a trading venue but where only a fraction of the whole order is displayed. When that fraction – for example 5,000 shares – finds a match, the next fraction of the order is immediately displayed.