to both passenger and mineral traffic between Sunderland Town Moor, and collieries at Hetton-le-Hole and Haswell in 1836, competing directly with the HD&R for coal traffic from the latter. However, it was the D&SR which constructed the first significant north–south section of the Durham Coast Line, that between Ryhope Grange Junction and Ryhope. In conjunction with the HD&R, the D&SR thus enabled passengers to travel between Sunderland and Hartlepool for the first time by rail, although passengers had to change stations at Haswell at the time. Tyne to Tees rail passenger travel then quickly became possible (with three changes of station) following the opening of Brandling Junction Railway between Oakwellgate (Gateshead) and Wearmouth (Monkwearmouth) on 5 September 1839 and the Stockton & Hartlepool Railway between the Clarence at , and a new terminus near West Hartlepool docks on 10 February 1841. The opening of the High Level Bridge over the River Tyne on 27 September 1849 subsequently extended this route through to . On its opening on 15 May 1852, the Leeds Northern Railway linked directly to the Clarence and, in doing so, provided the route with a link to the south. One year after the LNR reached Stockton, the newly created West Hartlepool Harbour & Railway (now owners of the Clarence lines) began to share the LNR station at North Stockton. The last of the independent railways that became part of the modern DCL was the Londonderry, Seaham & Sunderland Railway of 1854, constructed, primarily, to enable coal traffic from the extensive Londonderry Railway colliery railway network to be diverted from Seaham Harbour (which had become unable to handle the large volumes of coal passing through it) to the recently constructed South Dock at Sunderland and thus followed route which parallel the D&SR north of Ryhope. Like the rest of the railways discussed here, the LS&SR later introduced a passenger service on 2 July 1855 between Seaham and Hendon Burn. Amalgamations and the creation of a through route The Clarence had struggled financially, almost continuously since its construction began, and so the more successful Stockton & Hartlepool Railway took out a 21-year lease on it in 1844 which became permanent in 1851. The two companies were then formally amalgamated together and with the West Hartlepool Harbour & Dock Company on 17 May 1853, to form the West Hartlepool Harbour & Railway. Meanwhile, as part of its expansion, Newcastle &