The LSE acquired Sri Lanka's MillenniumIT for around £18 million in 2009 as it sought to catch up with nimble, technologically superior competitors such as Chi-X and Bats Europe.

The exchange boasted that Millennium Exchange would slash trading speeds to less than a millisecond from the 2.7 milliseconds produced by its expensive TradElect system, making it an attractive venue to the lucrative high-frequency trading community.

Initially the UK cash markets were slated to migrate last September before a postponement to November. However, an outage at the already migrated Turquoise system forced another delay while an investigation was conducted. Although sabotage was mooted as a possible reason, the problem was put down to human error.

Antoine Shagoury, CIO, LSE, says: "Today's roll-out of Millennium Exchange for our UK cash markets demonstrates our continued commitment to technological innovation in the marketplace. We are confident that this new platform will provide our customers with exceptional levels of performance, functionality, and capacity."

The LSE highlighted the importance of MillenniumIT and technology in general when it revealed plans last week to merge with Canada's TMX Group with the pair saying they intend to "operate on common world-class technology platforms".

LSE chief Xavier Rolet also predicts that over 30% of the combined revenues will come from technology and information services, claiming there is a "massive opportunity" for the group to take on Nyse Euronext and Nasdaq OMX as a provider of IT systems to bourses in emerging markets. The Johannesburg Stock Exchange has already licensed MillenniumIT.