Progress on Jubilee line upgrade
He described the project as reaching 'a significant milestone' ahead of the automatic signalling system's full installation which is on schedule to be completed in the spring.
The new system now operates between Stratford and Dollis Hill, and work is under way to extend it across the whole line.
When this happens, passengers can expect to see improvements with faster and more reliable trains.
Capacity will be boosted by 33 per cent - the equivalent of carrying around 5,000 extra passengers each hour - and journey times will be reduced by 22 per cent.
When Transport for London (TfL) acquired Tube Lines, the contractor for the Jubilee, Northern and Piccadilly lines in June last year, the upgrade was behind schedule.
Since then, London Underground (LU) has been working hard to complete the project.
Mayor of London, Boris Johnson, said: 'Parts of our Tube network date back to the 19th century and upgrading it is vital to ensure our Capital can continue to cope with ever increasing demands on public transport and maintain our role as the engine of the UK economy.
'Work has been progressing swiftly since TfL took control of Tube Lines and we can now see real milestones being reached, including the long-awaited completion of this crucial upgrade in just a few months time.
'This is good news for the many thousands of passengers who rely on the line, and clearly demonstrates how our hands-on approach to the upgrades is making real improvements.'
Mike Brown, LU's Managing Director, said: 'We inherited a Jubilee line upgrade that had been frustrating and painful for passengers and businesses, and we have been working around the clock to complete the work as quickly as possible.'
For more on the Jubilee line upgrade visit tfl.gov.uk/transform