Oxford will enjoy a service of four off-peak trains to and from London every hour on weekdays from December -- including two 125mph limited-stop expresses, with extra services in the peak hours.

The changes come as part of a radical overhaul of the Great Western main line timetable, affecting all First Great Western and FGW Link services from Paddington.

The aim is to make the best use of the four-track section between Didcot and London, by reserving the fast lines for 125mph expresses and switching 90mph Thames Turbo units to the slower parallel lines.

FGW plans to use its 125mph Adelante trains on most Oxford-London services, with a journey time of 52 minutes compared with 60 minutes on a Turbo express.

FGW InterCity 125 units on services to and from Hereford, via the Cotswold Line through west Oxfordshire, will provide some peak services.

Adelante units will take over most Cotswold Line services to and from Worcester, which serve Hanborough, Charlbury and Kingham.

A few Turbos will remain on the route, mainly on off-peak services between Oxford and Worcester.

Expresses will leave Oxford for London on the hour and at 30 minutes past the hour, with the stopping services filling in the gaps. In the reverse direction, the expresses will leave Paddington at 22 and 52 minutes past the hour. The stopping trains will depart at four and 34 minutes past the hour.

FGW spokesman Tim Bowcock said: "Passengers in Oxfordshire will see more reliable, faster services as a result of these changes."

However, the FGW Link stopping service between Oxford and Banbury -- serving Tackley, Heyford and Kings Sutton -- will suffer some cuts.

Mr Bowcock said: "The service will be slimmed down outside the peak hours. Most passengers on the route use the half-hourly Virgin CrossCountry expresses between Oxford and Banbury."

The Turbo units displaced by the Adelantes will be switched to other FGW Link services to provide extra seats in the peak hours, particularly between Reading and London, to help ease pressure on trains which start their journeys in Oxfordshire or further afield.

The new-look timetable will come into force on Sunday, December 12.

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FGW spokesman Tim Bowcock said: "We're still in the process of finalising the new timetable with Network Rail. Further talks are due within the next fortnight."