The London Stock Exchange has postponed the launch of its Linux-based IT system for cash markets, after a third live test was completed with customers over the weekend.

The Millennium Exchange system – built in a C++ environment around Linux, linked into Oracle databases – had been due to be switched on today.

It is now expected to go live on or around the contingency date of 15 November. But an exact date has not yet been decided.

The LSE has billed the system as the fastest in the world, with 126 microsecond trading times. Speed is crucial as brokers trade automatically and at lightning speed, using advanced algorithms.

The open-source based system will replace Microsoft .Net centred technology, and has been operational for one month in the exchange’s Turquoise dark pool, or anonymous, trading site.

Sources said that this weekend's third ‘dress rehearsal’, or live test on the cash markets, was largely successful. The additional test was added after some of the LSE’s 300 customers – trading firms – said they needed more time to test their systems on the new platform.

During the test, firms attempted logon, order entry, execution and other message interaction, and were encouraged to enter "high volumes" of messages in order to "fully test the performance of their applications", the LSE said in market documentation. The exchange also tested its fail-over to another datacentre, which would take over in the event of a problem on its main hardware.

Last Thursday there were some “configuration” issues on the Early Access Service, used by customers setting up their connections, that were rectified later in the day. The issues are understood to be the result of an information entry error rather than a technology problem.

The switch-on of Linux on the LSE’s cash markets is a major event for the exchange. David Lester, chief executive at Turquoise, has said the introduction of the fast platform demonstrates the LSE has “made it clear we intend to compete, and compete strongly”.

An announcement is expected this week on the go-live date for Linux.