Editing Great Western Railway (section)

===Route of the line===
This was by far Brunel's largest contract to date. He made two controversial decisions. Firstly, he chose to use a broad gauge of {{RailGauge|7ft}} to allow for the possibility of large wheels outside the bodies of the rolling stock which could give smoother running at high speeds. Secondly, he selected a route, north of the [[North Wessex Downs|Marlborough Downs]], which had no significant towns but which offered potential connections to [[Oxford]] and [[Gloucester]]. This meant the line was not direct from London to Bristol. From Reading heading west, the line would curve in a northerly sweep back to Bath.{{sfn|MacDermot|1927|at=Chapter 1}}

Brunel surveyed the entire length of the route between London and Bristol himself, with the help of many, including his solicitor, Jeremiah Osborne of the Bristol law firm [[Osborne Clarke]], who on one occasion rowed Brunel down the River Avon to survey the bank of the river for the route.<ref name="Clifton RFC">{{cite web |url=http://www.cliftonrfchistory.co.uk/captains/press/press.htm |website=Clifton Rugby Football Club History |title=Edward Payne Press |access-date=22 March 2012 |archive-url=https://web.archive.org/web/20120723122827/http://www.cliftonrfchistory.co.uk/captains/press/press.htm |archive-date=23 July 2012 |url-status=live }}</ref><ref name="Brunel 200 - Working With Visionaries" >{{cite web |url=http://www.brunel200.com/downloads/osborne_clarke_leaflet.pdf |title= Working With Visionaries |website=Brunel 200 |publisher=Osborne Clarke |access-date=22 March 2012 |archive-url=https://web.archive.org/web/20130520183659/http://www.brunel200.com/downloads/osborne_clarke_leaflet.pdf |archive-date=20 May 2013 |url-status=live }}</ref>

[[G. T. Clark|George Thomas Clark]] played an important role as an engineer on the project, reputedly taking the management of two divisions of the route including bridges over the [[River Thames]] at [[Gatehampton Railway Bridge|Lower Basildon]] and [[Moulsford Railway Bridge|Moulsford]] and of [[Paddington Station]].<ref>{{cite ODNB| last =James| first =B Ll| title =Clark, George Thomas (1809–1898)| year =2004| doi =10.1093/ref:odnb/5461| url =http://www.oxforddnb.com/view/article/5461| access-date =21 August 2007| archive-url =https://web.archive.org/web/20150924160253/http://www.oxforddnb.com/view/article/5461| archive-date =24 September 2015| url-status =live}}</ref> Involvement in major earth-moving works seems to have fed Clark's interest in geology and [[archaeology]] and he, anonymously, authored two guidebooks on the railway: one illustrated with [[lithograph]]s by [[John Cooke Bourne]];<ref name="Bourne" /> the other, a critique of Brunel's methods and the broad gauge.<ref>{{cite journal| last = Clark| first = GT| author-link = G. T. Clark |title=The Birth and Growth of the Broad Gauge| journal = Gentleman's Magazine| issue = 279| pages = 489–506| year = 1895}}</ref>

[[File:Sonning cutting.jpg|right|thumb|alt=A trestle bridge on four piers spans a cutting over two rail tracks|The [[Sonning Cutting]] in 1846]]
The first {{convert|22+1/2|mi|km|0}} of line, from Paddington station in London to [[Taplow railway station|Maidenhead Bridge station]], opened on 4 June 1838.{{sfn|MacDermot|1927|at=Chapter 2}} When [[Maidenhead Railway Bridge]] was ready the line was extended to {{Stnlnk|Twyford}} on 1 July 1839 and then through the deep [[Sonning Cutting]] to {{Stnlnk|Reading}} on 30 March 1840.{{sfn|MacDermot|1927|at=Chapter 4}} The cutting was the scene of [[Railway accident at Sonning Cutting|a significant accident]] two years later when a goods train ran into a [[landslip]]; ten passengers who were travelling in open trucks were killed. This prompted [[Parliament of the United Kingdom|Parliament]] to pass the [[Railway Regulation Act 1844]], requiring railway companies to provide better carriages for passengers.{{sfn|MacDermot|1927|at=Chapter 13}}

[[File:Cheffin's Map - Route of Great Western Railway, 1850.jpg|thumb|left|Route of the Great Western Railway on [[Charles Cheffins|Cheffin's Map]], 1850. The sweep to the north from Reading is clearly seen.]]

The next section, from Reading to {{Stnlnk|Steventon}} crossed the Thames twice and opened for traffic on 1 June 1840. A {{convert|7+1/4|mi|km|0|adj=on}} extension took the line to [[Challow railway station|Faringdon Road]] on 20 July 1840.{{sfn|MacDermot|1927|at=Chapter 4}} Meanwhile, work had started at the Bristol end of the line, where the {{convert|11+1/2|mi|km|0|adj=on }} section to [[Bath Spa railway station|Bath]] opened on 31 August 1840.{{sfn|MacDermot|1927|at=Chapter 5}}

On 17 December 1840, the line from London reached a temporary terminus at {{Stnlnk|Wootton Bassett Road}} west of Swindon and {{convert|80.25|mi|km|0}} from Paddington. The section from Wootton Bassett Road to {{Stnlnk|Chippenham}} was opened on 31 May 1841, as was [[Swindon railway station|Swindon Junction station]]{{sfn|MacDermot|1927|at=Chapter 4}} where the [[Cheltenham and Great Western Union Railway]] (C&GWUR) to [[Cirencester Town railway station|Cirencester]] connected. That was an independent line worked by the GWR, as was the [[Bristol and Exeter Railway]] (B&ER), the first section of which from Bristol to {{Stnlnk|Bridgwater}} was opened on 14 June 1841. The GWR main line remained incomplete during the construction of the {{convert|1|mi|1452|yd|km|2|adj=on}} [[Box Tunnel]], which was ready for trains on 30 June 1841, after which trains ran the {{convert|152|mi|km}} from Paddington through to Bridgwater.{{sfn|MacDermot|1927|at=Chapter 5}} In 1851, the GWR purchased the [[Kennet and Avon Canal]], which was a competing carrier between London, Reading, Bath and Bristol.{{sfn|MacDermot|1927|at=Chapter 7}}

The GWR was closely involved with the C&GWUR and the B&ER and with several other broad-gauge railways. The [[South Devon Railway Company|South Devon Railway]] was completed in 1849, extending the broad gauge to [[Plymouth Millbay railway station|Plymouth]],{{sfn|MacDermot|1931|at=Chapter 6}} whence the [[Cornwall Railway]] took it over the [[Royal Albert Bridge]] and into [[Cornwall]] in 1859{{sfn|MacDermot|1931|at=Chapter 7}} and, in 1867, it reached {{Stnlnk|Penzance}} over the [[West Cornwall Railway]] which originally had been laid in 1852 with the {{RailGauge|ussg}} [[standard gauge]] or "narrow gauge" as it was known at the time.{{sfn|MacDermot|1931|at=Chapter 8}} The [[South Wales Railway]] had opened between {{Stnlnk|Chepstow}} and {{Stnlnk|Swansea}} in 1850 and became connected to the GWR by Brunel's [[Chepstow Railway Bridge|Chepstow Bridge]] in 1852. It was completed to {{stnlnk|Neyland}} in 1856, where a transatlantic port was established.{{sfn|MacDermot|1927|at=Chapter 11}}

There was initially no direct line from London to Wales as the tidal [[River Severn]] was too wide to cross. Trains instead had to follow a lengthy route via Gloucester, where the river was narrow enough to be crossed by a bridge. Work on the [[Severn Tunnel]] had begun in 1873, but unexpected underwater springs delayed the work and prevented its opening until 1886.<ref name="Walker">{{cite book| last = Walker| first = Thomas A| title = The Severn Tunnel: Its Construction and Difficulties (1872–1887)| publisher = Nonsuch Publishing Ltd| year = 2004| location = Stroud| isbn = 1-84588-000-5}}</ref>