It served the village of Letterston 1 mile to the south east, and on railway maps was suffixed for St David's.

[1] However, there was a signal box at Wolf's Castle, because although most of the route was built as double track, a portion near the middle, which included Spittal Tunnel and the cutting through Treffgarne Gorge, was single-track, and it was necessary to have signal boxes at each end of the single-track section.

[2] The single-track section was later doubled, but although the temporary signal boxes at Spittal and Treffgarne closed with the introduction of full double-track working on 17 December 1906, Wolf's Castle signal box was retained to break the section, allowing two trains to proceed in the same direction between Clarbeston Road and Letterston simultaneously; there was also a crossover.

[4] The service was operated using GWR steam rail motors running between Fishguard Harbour and Neyland; there were three trains a day in each direction.

Falling traffic on the line caused it to be reduced to single-track on 16 May 1971 with a passing loop at Letterston Junction.