Darlington Junction Railway had taken over the BJR on 1 September 1844, and then purchased the D&SR in 1846. Following its amalgamation with the Great North of England Railway, the Newcastle & Darlington Junction Railway became the York & Newcastle Railway, and took out a lease on the HD&R before both became part of the York, Newcastle & Berwick Railway under an Act of 22 July 1848. Finally, in 1854, the YN&BR, LNR, and York & North Midland Railway were amalgamated to form the North Eastern Railway which eventually absorbed the WHH&R in 1865. Thus, from 1865, one company was in control of the whole through route between Middlesbrough, Hartlepool, Sunderland and Newcastle, although the lines remained largely unconnected. Thus a series of improvements were initiated by the NER to better integrate is fragmented network. For the DCL, one of the first of these saw the construction of a new curve to link the ex-LNR Stockton branch to the former network of Stockton & Darlington Railway (absorbed by the NER in 1863), which linking Middlesbrough to lines towards Stockton and Hartlepool. Combined with the 1873 realignment of the south to east curve at Norton Junction, which eased the severity of its curvature, this massively improved the connections between Hartlepool and the rest of the Teesside region. The rope-worked 1 in 34 incline at Bank was realigned in 1874 to reduce the gradient to that of 1 in 52 and thus enable locomotive working over the entire Hartlepool-Sunderland route. In 1877, the NER constructed a new chord between the ex-HD&R and ex-D&SR lines at Haswell and replaced the previously separate terminus stations with a new through station. In the same year, at Hartlepool, they also constructed a direct link between the ex-HD&R and former Stockton & Hartlepool Railway lines which skirts around the western edge of the docks and replaced a more circuitous link through them. Both the ex-Stockton & Hartlepool Railway and ex-HD&R termini were replaced by new stations at West Hartlepool (in 1880) and Hartlepool (in 1878), respectively. However, of these links constructed by the NER, arguably the most significant was the Monkwearmouth Junction Line of 1879 which linked the ex-D&SR lines at Ryhope Grange Junction to the ex-BJR lines at Monkwearmouth. This involved the construction of the Monkwearmouth Railway Bridge over the River Wear, a new station at Sunderland Central, and tunnels on either side of the station.