There was some revival in colliery activity after World War II but most of the traffic had ceased in 1969 and the line finally closed completely in 1989.

However, in the following months there was a major upheaval in the NBR board due to shareholder dissatisfaction, and none of the "Lasswade" railways was built.

[1][page needed] During this period it was evident that further mineral extraction was developing, and a special meeting of shareholders on 5 February 1872 approved the submission of a bill to extend the line to Glencorse and Mauricewood.

[note 2][4][page needed] The Shotts Iron Company pit at Mauricewood was on high ground and was reached from the railway branch by a tramway on an inclined plane.

[7][page needed] It was not until 22 July 1874 that Colonel Rich of the Board of Trade made a formal inspection; there were some qualifications in his report, in particular over the method of working, but sanction was later given by letter, on 1 August 1874, after the company gave written undertakings about the signalling arrangements, and the section from Loanhead to Roslin may have opened on 23 July 1874.

In 1875, the Shotts Iron Company sunk a new shaft at Greenlaw near Glencorse Barracks, and (encouraged by the NBR) the ELRR sought parliamentary authority to extend the line to serve the mine.

[5][page needed] Construction of the extension to Glencorse was heavily delayed due to problems with the embankments.

On 16 May 1877 Major General Hutchinson inspected the extension, and criticised the absence of block instruments for signalling trains; there had been no decision by the company on the method of working, and an undertaking was required from the NBR (as intended purchasers of the line) as well as from the Edinburgh, Loanhead and Roslin Railway Company.

[5][page needed] The Greenlaw colliery tramway was transferred a short distance to the west, bringing the coal from Mauricewood Colliery (a new shaft connected to the Greenlaw workings) to the main line nearer the Gas Works end of the line; this took place some time between 1878 and 1894.

In the late 1880s the mansion house of Drydenbank, near Bilston Glen Viaduct, collapsed, having been undermined by coal working.

The first bus service from Roslin to Edinburgh started in 1914, immediately affecting passenger carryings on the line.

At that time, the line was cut back to a point immediately south of Glencorse station, to continue to serve the Barracks, but the line was again shortened to Roslin from 31 August 1959, and only mineral traffic continued on the branch, the ordinary goods facilities at Gilmerton, Roslin and Glencorse being withdrawn.

Bilston Glen Colliery opened in April 1961; at the time this was a modern show-piece for the National Coal Board, and further mineral traffic was brought to the line.

Roslin colliery closed in January 1969 and the line was abandoned from the north end of Bilston viaduct southwards.