The UK's Network Rail has completed the final track installations on the line that connects Oxford city centre with London Marylebone.
Under the £320m project, a team of engineers have transformed the old 20mph-40mph branch route into a 100mph main line.
Out of the total project cost, £130m has been provided by Chiltern Railways. The project was originally announced in 2002 and eventually approved in 2013.
Network Rail London North Western route managing director Martin Frobisher said: "This important landmark in our nationwide Railway Upgrade Plan will offer a great new travel option not just for business and leisure passengers in Oxford going to London but also for those in London heading to Oxford.
“It will bring economic benefits to the Oxford region and with it new opportunities for people living there."
The final track installations were completed around Peartree and Wolvercote in Oxford, Network Rail said in a statement.
Chiltern Railways will offer services from Oxford city centre, starting from 12 December this year.
Two trains an hour will run throughout the day on the route, with journey times cut to an hour.
Chiltern Railways managing director Dave Penney said: “The new rail line will bring significant social, economic and environmental benefits to those living and working along the route and will be the completion of first new rail link between a major British city and London for over 100 years.”
Image: Final track installations have been completed on the upgraded line that links Oxford city centre and London Marylebone. Photo: © Network Rail.