It had reached St Davids station in Exeter in 1844 and was allied with the Great Western Railway (GWR) with which it connected at Bristol, forming a continuous route from London.

The E&CR branched off the B&ER main line at Cowley Bridge, some distance north of the St Davids station, and the NDR was an extension of it at Crediton.

[8][page needed] At this time Devonport and Stonehouse were independent towns and the former, with its naval dockyards, was an important traffic source.

To reach their station they used the 'Cornwall Loop', a newly built connection from the SDR to the Cornwall Railway which avoided a reversal at their Plymouth Millbay terminus.

[9][page needed] Having obtained a foothold in both Plymouth and Devonport, the LSWR now set about improving its facilities in the area so that it could reduce its dependency on the broad gauge companies.

[7][page needed] In 1880 it made another line from near Friary to the Plymouth and Dartmoor Railway's old 4 ft 6 in (1,372 mm) gauge route to Cattewater, which gave it access to more quays.

Meanwhile, on the other side of Plymouth, the Stonehouse Pool Improvement Company had been formed to create a quay that large vessels could use at all states of the tide.

It proposed to build a railway connection to Devonport station which the LSWR agreed to rent, and this opened for freight traffic on 1 March 1886.

In 1882 an Act of Parliament was passed to allow the construction of independent lines alongside the GWR route from Lydford to a new station in the centre of Plymouth.

This scheme was replaced the following year by that of another independent company supported by the LSWR, the Plymouth, Devonport and South Western Junction Railway (PD&SWJR).

This obtained its Act on 25 August 1883 for a new railway from Lidford which would pass to the west of Tavistock then down the valley of the River Tamar to reach Plymouth.

Competition from tramways in Plymouth and Devonport in the first decade of the twentieth century spurred the company into constructing several new stations in the towns and running an intensive suburban railmotor service.

[8][page needed] The GWR had amalgamated with the B&ER, SDR and Cornwall Railway during the 1870s and 1880s, and converted their lines to standard gauge in 1892.

In the weeks before the conversion, some of the new rolling stock required was worked over the LSWR to reach the Plymouth area, and during the two days that the line was closed they also sent the important London mail trains by this route.

[8][page needed] Devonport station closed on 7 September 1964 and trains were diverted to the former GWR route between Plymouth and St Budeaux.

[8][page needed] Until 2019, heritage trains of the Dartmoor Railway operated between Meldon Quarry, Okehampton and Sampford Courtenay at other times.

In 2021 the line as far as Okehampton was transferred to Network Rail, the track relaid and structures repaired,[16] and a regular seven-days-a-week GWR service from Exeter was resumed, increasing to hourly in 2022.

From here to Yeoford it follows river valleys,[4][page needed] but the next stage of the route, through Okehampton and Lydford, takes it around the northern edge of Dartmoor.

[5][page needed] The PD&SWJR route into Plymouth followed the valley of the River Tamar but still involved much heavy engineering with gradients as steep as 1 in 73.

[11][page needed] On the GWR section the line crossed the viaduct which carries the Cornwall Loop near North Road station, and dives through Mutley Tunnel.