Editing Chiltern Main Line (section)

===Early history and construction===
What is now the Chiltern Main Line was built in three key phases by the [[Great Western Railway]] (GWR) between 1852 and 1910:
* The first phase was the [[Birmingham and Oxford Junction Railway]] opened in 1852. The route ran from {{Stnlnk|London Paddington}} to Birmingham Snow Hill; in 1854, it was extended to [[Wolverhampton Low Level railway station|Wolverhampton Low Level]] and, connecting with other GWR lines, became the southern leg of a longer distance route to {{rws|Shrewsbury}}, {{rws|Chester}} and [[Birkenhead Woodside railway station|Birkenhead]]. It ran via the [[Great Western Main Line]] to {{stnlink|Didcot}} and then via {{Stnlnk|Oxford}}, {{rws|Banbury}} and Leamington Spa. This route was circuitous and was {{convert|16|mi|km}} longer between London and Birmingham than the rival [[London and North Western Railway]]'s [[Euston railway station|Euston]]-[[Birmingham New Street railway station|New Street]] route via {{rws|Rugby}}, meaning that the GWR could not compete on journey times.<ref>{{cite book |last=MacDermot |first=E.T.|year=1927 |title=History of the Great Western Railway, volume I 1833–1863 |location=London |publisher=Great Western Railway; Reprinted 1982, Ian Allan |isbn=0-7110-0411-0 |page=327, 336}}</ref><ref>{{cite book |last1=Boynton |first1=John |title=Main Line to Metro: Train and tram on the Great Western route: Birmingham Snow Hill – Wolverhampton |date=2001 |publisher=Mid England Books |isbn=978-0-9522248-9-1 |page=18}}</ref>
* The second phase was completed in 1906. In order to create a more direct route, the GWR collaborated with the [[Great Central Railway]] (GCR) to create a new railway known as the [[Great Western and Great Central Joint Railway]] between Northolt (in north-west London) and Ashendon Junction (west of [[Aylesbury]]) via {{rws|High Wycombe}}.<ref name="Jenkins">{{cite book |last=Jenkins |first=Stanley C. |title=The Great Western and Great Central Joint Railway |date=20 July 2006 |publisher=The Oakwood Press |isbn=9780853616535}}{{Page needed|date=May 2023}}</ref>
* Thirdly, as a final development, the GWR opened the ''Bicester cut-off line'' in 1910; this was an {{convert|18+1/4|mi|km|abbr=on}} connection between the Great Western and Great Central Joint Railway at Ashendon Junction, via {{rws|Bicester North}}, to Aynho Junction on the Birmingham line south of Banbury. This shortened the route between London and Birmingham by {{convert|18+1/2|mile|km}}, compared to the original Oxford route, and reduced the fastest London-Birmingham journey times by 20 minutes (from 140 to 120 minutes). Most of the through trains were immediately transferred to the new route, although the original route via Oxford continued in use and is now known as the [[Cherwell Valley line]].<ref name="Jenkins"/>
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 | caption1 = The Birmingham and Oxford Junction Railway as built in 1852. Prior to the construction of the Bicester cut-off line in 1910, London to Birmingham trains had to run on the [[Cherwell Valley line|circuitous route]] via [[Oxford]].
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 | caption2 = The Great Western and Great Central Joint Railway (red) and the Bicester cut-off line (yellow) opened in 1906 and 1910 respectively. This completed the route of what is now the Chiltern Main Line.
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