Editing Great Western Main Line (section)

==History==
===Construction===
The construction of what would become the GWML was motivated by several factors, one of the more influential being the sizeable merchant community of Bristol, which keenly advocated for such a railway to be built to help maintain the city's position as the second port of the country as well as the chief one for American trade.<ref>{{Cite book |last = Channon |first = Geoffrey |url = https://archive.org/details/bha062 |title = Bristol and the Promotion of the Great Western Railway, 1835 |isbn = 0-901388-45-9 |publisher = Bristol Historical Association |year = 1985 |location = Bristol, UK |publication-date = 1985 |language = en-GB}}</ref> More specifically, fearing rising competition from [[Liverpool]] and railway developments to its favour, the sought railway was to be preferably built to superior standards as to out-perform any of the lines serving the [[North West England|North West of England]].<ref name="MacD1-1">{{harvnb|MacDermot|1927|loc=chapter 1}}</ref> Thus, the line built by the [[Great Western Railway]] and engineered by [[Isambard Kingdom Brunel]] was originally a dual track line using a wider {{track gauge|84in|lk=on}} [[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> The line's construction costs were considerably higher due to the use of this broad gauge.<ref name = "first hsr2019"/>

The route of the GWML includes dozens of [[listed building]]s and structures, including tunnel portals, bridges and viaducts, stations, and associated hotels.{{sfn|Sanderson | Pollard | Thorne | Hradsky |2012}} Part of the route passes through and contributes to the [[Georgian Architecture]] of the [[City of Bath]] World Heritage Site; the path through [[Sydney Gardens]] has been described as a "piece of deliberate railway theatre by Brunel without parallel".{{sfn|Sanderson | Pollard | Thorne | Hradsky |2012|loc = MLN1 10605, MLN1 10605, MLN1 10605, MLN1 10610, MLN1 10614, MLN1 10618}} [[Grade I]] listed structures on the line include [[London Paddington]], [[Wharncliffe Viaduct]], the 1839 Tudor gothic [[Avon Bridge|River Avon Bridge]] in Bristol, and [[Bristol Temple Meads railway station|Bristol Temple Meads station]].{{sfn|Sanderson | Pollard | Thorne | Hradsky |2012| loc = MLN1 0000 , MLN1 0742, MLN1 11725, MLN1 11826 }}<ref name = "first hsr2019"/>

The line was opened in stages between 1838 and 1841.<ref>{{harvnb|MacDermot|1927|pp=130–131}}</ref> The first section, between Paddington and [[Taplow railway station|Maidenhead Bridge]] opened on 4 June 1838; the final section, between Chippenham and Bath, was opened on completion of the [[Box Tunnel]], the longest railway tunnel driven by that time, in June 1841.<ref>{{cite web |url = http://www.british-history.ac.uk/vch/wilts/vol4/pp280-293 |title = Victoria County History: Wiltshire: Vol 4: Railways |year = 1959 |editor-last = Crittall |editor-first = Elizabeth |website = british-history.ac.uk |publisher = University of London |access-date = 27 December 2017 |archive-date = 16 July 2021 |archive-url = https://web.archive.org/web/20210716084149/https://www.british-history.ac.uk/vch/wilts/vol4/pp280-293 |url-status = live |language = en-GB}}</ref><ref>{{cite book |last = Swift |first = Andrew |title = The Ringing Grooves of Change |year = 2006 |publisher = Akeman Press |isbn = 0-9546138-5-6 |pages = 215–249 }}</ref> The line's alignment was so level and straight it was nicknamed "Brunel's billiard table".<ref name = "first hsr2019">{{cite magazine |title = The Great Western: the world's first high speed railway |first = Gareth |last = Dennis |magazine = Rail |issue = 873 |date = 27 February 2019}}</ref>

===Changes under the Great Western Railway===
The track was supplemented with a third rail for [[dual gauge]] operation, allowing standard gauge {{track gauge|uksg}} trains to also operate on the route, in stages between 1854 and 1875. Dual gauge was introduced as follows: London to [[Reading railway station|Reading]] (October 1861), Reading to {{rws|Didcot}} (December 1856), Didcot to {{rws|Swindon}} (February 1872), Swindon to Thingley Junction, {{rws|Chippenham}} (June 1874), Thingley Junction to {{rws|Bathampton}} (March 1875), Bathampton to Bristol (June 1874), Bristol station area (May 1854). The broad gauge remained in use until 1892, at which point the last 500 miles of track were converted to standard gauge.<ref name = "first hsr2019"/><ref>{{cite book |last = Clinker |first = C. R. |title = New light on the Gauge Conversion |year = 1978 |publisher = Avon-Anglia |location = Bristol, UK |isbn = 0-905466-12-8 |pages = 15–16 }}</ref>

Between 1877 and 1899, the original dual tracks were widened to four in numerous places, mainly in the east half of the line: Paddington to {{rws|Southall}} (October 1877), Southall to {{rws|West Drayton}} (November 1878), West Drayton to {{rws|Slough}} (June 1879), Slough to east side of [[Maidenhead Railway Bridge|Maidenhead Bridge]] (September 1884), Maidenhead Bridge to {{rws|Reading}} (June 1893), Reading station (1899), Reading to {{rws|Pangbourne}} (July 1893), Pangbourne to [[Cholsey railway station|Cholsey and Moulsford]] (June 1894), Cholsey and Moulsford to [[Didcot Parkway railway station|Didcot]] (December 1892); also short sections between Didcot and Swindon, and at Bristol.{{citation needed|date=December 2016}}

Following the [[Slough rail accident]] of 1900, in which five passengers were killed, improved [[vacuum brake|vacuum braking]] systems were used on locomotives and passenger rolling stock; furthermore, [[Automatic train control#United Kingdom|Automatic Train Control]] (ATC) was introduced in 1908.<ref name="Derail">{{cite book |last = Faith |first = Nicholas |date = 2000 |title = Derail: Why Trains Crash |location = London, UK |publisher = [[Channel 4]] |page = 53 |isbn = 9780752271651}}</ref>

Further widenings of the line took place between 1903 and 1910; another round of widening works occurred between 1931 and 1932.{{sfn|Sanderson | Pollard | Thorne | Hradsky |2012| page = 6 }} By the 1930s, trains traversing the GWML were reportedly attaining the highest average speeds in the world.<ref name = "first hsr2019"/>

A legacy of the broad gauge was that trains for some routes could be built slightly wider than was normal in Britain; examples included the 1929-built ''[[GWR Super Saloons|Super Saloons]]'' used on the [[boat train]] services that conveyed transatlantic passengers to London in luxury.<ref>{{cite book |last = Harris |first = Michael |title = Great Western Coaches From 1890 |publisher = David and Charles |year = 1985 |edition = 3rd |location = Newton Abbot |isbn = 0-7153-8050-8 |page = 83}}</ref> When the company celebrated its centenary during 1935, new "Centenary" carriages were built for the Cornish Riviera Express, which again made full use of the wider [[loading gauge]] on that route.<ref>{{harvnb|Harris|1985|page=95}}</ref>

At the outbreak of the [[First World War]] in 1914, the Great Western Railway, and thus the GWML, was taken into government control, as were most major railways in Britain. After the conflict, the companies were reorganised into the [[Big Four (British railway companies)|"big four" companies]], of which the Great Western Railway was one. The railways, including the GWML, returned to direct government control during the [[Second World War]] before being [[nationalisation|nationalised]] to form [[British Rail]]ways (BR) in 1948, thus bringing the line into public ownership.<ref>{{cite magazine |date = January–February 1948 |title = British Railways |magazine = [[The Railway Magazine]] |location = Westminster, UK |publisher = Railway Publishing Company |publication-date = 1 January 1948 |volume = 94 |issue = 573 |page = 72 |language = en-GB}}</ref><ref>{{cite magazine |date = March–April 1948 |title = The Minor British Railways and the Joint Lines |magazine = [[The Railway Magazine]] |location = Westminster, UK |publisher = Railway Publishing Company |publication-date = 1 March 1948 |volume = 94 |issue = 574 |page = 126 |language = en-GB}}</ref>

===British Rail era===
Unlike the other BR regions, which introduced [[diesel-electric]] locomotives, the [[Western Region of British Railways|Western Region]], to which the GWML belonged, decided to procure a complete range of [[diesel-hydraulic]] locomotives to fulfil its [[List of British Rail power classifications|type 1 to type 4]] power requirements. These included the [[British Rail Class 42|''Warship'']] locomotives, which were based on proven [[West German]] designs, the British-designed [[British Rail Class 14|Class 14]], [[British Rail Class 35|''Hymek'']] and [[British Rail Class 52|''Western'']] types. However, these were all eventually withdrawn and replaced with more standard British Rail diesel-electric classes such as the [[British Rail Class 37|Class 37]] and [[British Rail Class 47|Class 47]].

During the 1970s, the line speed of the GWML was upgraded to permit faster operations; this work was in preparation for the introduction of the [[InterCity 125]] high speed train (HST).<ref name='EarlyHighspeedBR'>{{cite journal |title = High speed track on the Western Region of British Railways |last = Collins |first = R.J. |journal = Proceedings of the Institution of Civil Engineers |year = 1978 |volume = 64 |issue = 2 |pages = 207–225 |publisher = [[Institution of Civil Engineers]] |doi = 10.1680/iicep.1978.2755 |language = en-GB}}</ref><ref name=bbc1976>{{cite news |title = New train speeds into service |url = http://news.bbc.co.uk/onthisday/hi/dates/stories/october/4/newsid_2486000/2486817.stm |access-date = 15 May 2019 |work = BBC News |date = 4 October 1976 |language = en-GB}}</ref> The HST brought about considerable improvements in service and reduced journey times.<ref>{{Cite news |last1 = Owen |first1 = A.D. |last2 = Phillips |first2 = G.D.A. |publisher = [[University of Bath]] |title = The Characteristics of Railway passenger demand |page = 234 |url = http://www.bath.ac.uk/e-journals/jtep/pdf/Volume_XX1_No_3_231-253.pdf |language = en-GB}}</ref><ref>{{cite news |url = http://news.bbc.co.uk/1/hi/england/berkshire/5407016.stm |title = High Speed Train marks 30 years |work = BBC News |access-date = 29 April 2009 |date = 4 October 2006 |first = Joe |last = Campbell |language = en-GB}}</ref>

In 1977, the Parliamentary Select Committee on Nationalised Industries recommended considering electrification of more of Britain's rail network and, by 1979, British Rail had presented a range of options that included electrifying the line from Paddington to Swansea by 2000.<ref>{{cite book |title = Railway Electrification |date = Winter 1979 |publisher = [[British Railways Board]] (Central Publicity Unit) |pages = 0–2, 8}}</ref> Under the [[Premiership of Margaret Thatcher|1979–90 Conservative governments]] that succeeded the [[Callaghan ministry|1976–79 Labour government]], the proposal was not implemented.

In the mid-1990s, the line between London Paddington and [[Hayes & Harlington railway station|Hayes & Harlington]] was electrified as part of the [[Heathrow Express]] scheme, which was officially launched in June 1998.<ref>{{Cite web |title = Heathrow Express |url = https://www.railway-technology.com/projects/heathrow-express/ |access-date = 30 June 2020 |website = Railway Technology |language = en-GB |archive-date = 15 August 2018 |archive-url = https://web.archive.org/web/20180815045612/https://www.railway-technology.com/projects/heathrow-express/ |url-status = live}}</ref><ref>{{cite news |date = 23 June 1998 |title = Heathrow Express takes off |url = http://news.bbc.co.uk/1/hi/uk/118180.stm |url-status = live |archive-url = https://web.archive.org/web/20201220201437/http://news.bbc.co.uk/2/hi/uk_news/118180.stm |archive-date = 20 December 2020 |access-date = 6 August 2016 |work = BBC News |language = en-GB}}</ref>

===Privatisation era===
As part of the [[privatisation of British Rail]], the Great Western [[InterCity (British Rail)|InterCity]] franchise was awarded by the [[Director of Passenger Rail Franchising]] to [[Great Western Holdings]] in December 1995, and it began operations on 4 February 1996.<ref>{{Cite news |url = https://www.theguardian.com/uk/1997/sep/20/alexbellos |title=The passenger train |last1 = Bellos |first1 = Alex |date = 20 September 1997 |work = The Guardian |location = London, UK |access-date=4 September 2020 |language = en-GB}}</ref><ref>{{cite web |url = http://www.parliament.uk/documents/commons/lib/research/rp99/rp99-080.pdf |title = Railway Organisations Research Paper 99/80 |publisher = House of Commons Library |date=20 September 1999 |language = en-GB}}</ref> Via multiple contract extensions, this operator, which currently trades as [[Great Western Railway (train operating company)|Great Western Railway]] has been the primary operator of passenger services on the GWML for multiple decades.<ref>{{cite press release |url = https://www.gov.uk/government/news/critical-rail-services-protected-in-new-deals-for-gwr-and-southeastern |title = Critical rail services protected in new GWR and Southeastern |publisher = Department for Transport |date = 30 March 2020}}</ref><ref>{{cite magazine |archive-url = https://web.archive.org/web/20200401051953/https://www.railwaygazette.com/uk/firstgroup-says-new-great-western-contract-has-appropriate-balance-of-risk-and-reward/56134.article |archive-date = 1 April 2020 |url = https://www.railwaygazette.com/uk/firstgroup-says-new-great-western-contract-has-appropriate-balance-of-risk-and-reward/56134.article |title = FirstGroup says new Great Western contract has appropriate balance of risk and reward |magazine = Railway Gazette International |location = London, UK |date = 30 March 2020}}</ref><ref>{{cite web |url = https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1122644/first-greater-western-ltd-2022-nrc.pdf |title = First Greater Western Limited 2022 national rail contract |publisher = Department for Transport |date = 14 June 2022 |access-date = 5 March 2023}}</ref>

In August 2008, it was announced that a number of speed limits on the relief lines between Reading and London had been raised, so that 86% of the line could be used at {{cvt|90|mph}}.<ref name="First Great Western Customer Panel">{{cite web |url = http://www.firstgreatwestern.co.uk/Documents/Custom/Customer%20panel/East%20Customer%20Panel%209.10.08%20minutes%20-%20WEBSITE.pdf |title = First Great Western Customer Panel |access-date = 24 November 2008 |publisher = [[First Great Western]] |archive-date = 11 October 2010 |archive-url = https://web.archive.org/web/20101011164756/http://firstgreatwestern.co.uk/Documents/Custom/Customer%20panel/East%20Customer%20Panel%209.10.08%20minutes%20-%20WEBSITE.pdf |url-status = dead |language = en-GB}}</ref>

By 2019, the partial electrification of the GWML permitted the replacement of InterCity 125 and {{brc|180}} sets by new [[Intercity Express Programme|Hitachi Super Express]] high speed trains – the {{brc|800}} and {{brc|802}}. The procurement programme for these trains, known as the [[Intercity Express Programme]], was highly impacted by the GWML's electrification scheme, particularly the abandonment of diesel-only trains in favour of bi-mode trains, which were elongated and outfitted with a second transformer to maximise their use of the electrified sections.{{sfn|Foster|2010|pp=14-15|loc = The IEP}}{{sfn|Foster|2010a|pp=26—27}} The electrification of the line also allowed the introduction of other rolling stock, such as {{brc|387}} [[electric multiple units]], to conduct shorter-distance services.<ref>{{Cite web |date = 24 March 2015 |title = Derby to build new trains for First Great Western |url = http://www.railnews.co.uk/news/2015/03/24-derby-to-build-new-trains.html |access-date = 2 January 2017 |website = railnews.co.uk |archive-date = 16 July 2021 |archive-url = https://web.archive.org/web/20210716084228/https://www.railnews.co.uk/news/2015/03/24-derby-to-build-new-trains.html |url-status = live |language = en-GB}}</ref>