The first attempt to connect the 120 miles (200 kms) between London and Bristol by railway was proposed in 1824, one year before the opening of the Stockton and Darlington Railway (generally regarded as the world's first railway). At the time, Bristol was the second most important city in England, after London. The scheme, which was for a freight railway, failed to attract enough sponsors and was soon abandoned.
Following the success of the Liverpool and Manchester Railway (the world's first passenger railway - opened in September 1830), a second scheme, proposing a passenger railway using a slightly more southerly route through Pewsey Vale was put forward in 1833, but again failed to attract enough sponsors.
In 1834, a further attempt to obtain an Act of Parliament to build a railway (to be called the Great Western Railway) was made by a group of businessmen and influential people. The directors appointed Isambard Kingdom Brunel as engineer, who recommended a route through the Vale of White Horse, similar to the route suggested in the 1824 proposal. The Bill was passed by the House of Commons in 1834, but was rejected by the House of Lords. Opposition to the Great Western Railway Bill had come from a number of influential lords who owned property near Vauxhall, one of the possible sites of the London terminus. Opposition had also come from the London and Southampton Railway, which succeeded in obtaining its Act in 1834 and wanted to secure the Bristol traffic by building a branch from its own line to Bristol.
Undeterred, the directors resubmitted a slightly modified Bill in 1835 which was passed into law. The cost of building the railway was estimated to be £2,800,000. Following the failure of the negotiations with the London and Birmingham Railway to share Euston station, Paddington was chosen as the location of the London terminus.
The issue of the railway's gauge was also decided in 1835. When the Liverpool and Manchester Railway was built, its engineer, Robert Stephenson, chose to build it to the same gauge as the Stockton and Darlington Railway (engineered by his father, George Stephenson). This gauge become known as "standard gauge" (4ft 8½ins). Brunel, however, successfully persuaded the directors of Great Western Railway that a wider gauge would be more suitable for the faster trains proposed between London to Bristol. The gauge was set at 7ft 0¼ins and the broad gauge was born.
Work began immediately and a number of officers appointed to the company. Among these was Daniel Gooch, who, in August 1837, at the age of 21, was appointed in charge of the locomotive department as Superintendent of Locomotive Engines. Work also began on two other railways which were to connect to the Great Western Railway - the Bristol & Exeter Railway and the Cheltenham & Great Western Union Railway. The line was opened in stages between 1838 and 1841. The first section finished was between London and Maidenhead (22 miles - 35 km), which opened for service on 4 June 1838 with 8 trains each way. In the first week of service 10,360 passengers were carried.
The final section of the 117 mile (187 km) London and Bristol line was opened on the 30 June 1841, by which time the Bristol and Exeter Railway had opened its line between Bristol and Bridgwater (33 miles - 53 km) and the Cheltenham and Great Western Union Railway had build a 17 mile (26 km) line from a junction at Swindon on the GWR line as far as Cirencester.
The July 1841 timetable lists 8 trains each way between London and Bristol (5 on Sundays) with additional trains between London and Maidenhead, and Bristol and Bath. The journey from London to Bristol took 4½ hours, except by the 3 mail trains in each direction which took about 15 minutes less. Connecting services enabled passengers to travel on from Bristol to Bridgwater and from Swindon to Cirencester.