The London Stock Exchange moved its main trading platform to a faster system just days after after launching a bid to buy Canadian exchange TMX.
The exchange has moved its main UK share system to technology provided by Millenium, a Sri Lankan company it bought in 2009, which makes it faster and more attractive to increasingly important trading by hedge funds.
The upgrade was postponed in November, when a trading glitch prompted the LSE to probe what went wrong amid speculation of sabotage.
The successful migration gives a boost to the exchange after it announced the deal with Toronto-based TMX.
Talks with TMX were overshadowed when Deutsche Boerse announced last week it was in advanced talks to buy NYSE Euronext, in a deal that would create the world's largest exchange group.
Ultra-fast and secure trading systems are crucial tools as stock exchanges try to attract high-frequency trading clients, hedge funds that make profits by dipping in and out of the market in fractions of a second.