Opening and original operation

The line was opened in 1850 as part of the Buckinghamshire Railway, which in 1879 became part of the London and North Western Railway. In the grouping of Britain's railways in 1923 the L&NWR became part of the London, Midland and Scottish Railway, and in the nationalisation of Britain's railways in 1948 the LMS became part of British Railways. Both the LMS and BR ran passenger services between Oxford and Cambridge via the Buckinghamshire Railway, Marston Vale line and Bedford and Cambridge Railway. This led to the Oxford - Cambridge route being informally called the Varsity line.

20th-century closure and reopening

In 1967 British Railways withdrew Oxford – Cambridge services and closed the section of line between Oxford and Bletchley. In 1987, Network SouthEast restored passenger services on the Oxford – Bicester Town section, on the initiative of Oxfordshire County Council. In 1988, Network SouthEast rebuilt and reopened Islip station, again with Oxfordshire County Council support.

Since 2005, an enhanced service including Sunday services has run during the weeks before Christmas, mainly for the Bicester Village Shopping Centre adjacent to Bicester Village Station (formerly Bicester Town station).

In May 2009, a partnership between First Great Western and Oxfordshire County Council rebranded and relaunched the line as The Bicester Link. On 22 May 2011, Chiltern Railways took over all passenger operations on the line. The line closed for upgrades in February 2014, instead running a replacement bus service about 15 times a day.

Evergreen 3

In August 2008 Chiltern Railways announced Project Evergreen 3 to create a new passenger service between Oxford and London Marylebone via High Wycombe by 2012. As part of this project Chiltern Railways would double most of the line, build a new Oxford Parkway passenger station at Water Eaton to serve Kidlington and north Oxford and build the short 'missing-link' from Bicester Town (now Bicester Village), station to the Chiltern Main Line. This was to give Oxford an alternative to Great Western Railway's rail link to London Paddington and provide Oxford with a direct rail-link to High Wycombe for the first time since British Railways closed the Princes Risborough - Oxford section of the Wycombe Railway in 1964.^[3]

Work on Evergreen 3 commenced with the closing of the line in February 2014. The works included complete reconstruction of the line to modern standards, with new track, signalling and bridges, and the infrastructure improvements ready for 'East West Rail' services (see below). The line was double tracked from Oxford North Junction to Bicester South Junction, upgraded for 100 mph (160 km/h) operation and prepared for electrification. Between Oxford station and Oxford North Junction the line uses the former 'Jericho' line, bi-directionally. A new 1 km chord has also been built at Bicester (from Bicester Gavray Junction, linking with the Chiltern main line at Bicester South Junction) and 37 level crossings have been eliminated.

Chiltern Railways commenced driver training on the upgraded line in September 2015, and the line between the new Oxford Parkway and Bicester Village stations reopened on 26 October 2015,^[4] with two trains per hour running between London Marylebone and Oxford Parkway. It was originally planned these would be extended to Oxford in March 2016,^[5] but services to Oxford started on 11 December 2016.^[6][7] Planning permission for the work at Oxford Station allowing the new platforms to be constructed was given on 1 December 2015.^[8]