The London Stock Exchange is expected to announce, possibly as early as Wednesday, the acquisition of Millennium IT, a Sri Lankan trading technology company, as the group embarks on a massive upgrade of its trading platform.

The move marks the biggest step yet taken by Xavier Rolet, chief executive, to dismantle the legacy of his predecessor Clara Furse. The exchange’s existing TradElect trading system was upgraded two years ago at a cost of £40m ($66m).