The 1963 Beeching Report proposed the entire Central Wales line be closed but this was refused by the MoT except for the Pontarddulais to Swansea Victoria section.

[2] As a rural branch line, it survived the Beeching Axe since it carried freight traffic, serving the steelworks at Bynea and industrial areas such as Ammanford and Pontarddulais, linking them with the docks at Llanelli.

For more than two years only two of the loops (Llandrindod and Llanwrtyd) were operational as Network Rail were unable to source spare parts for the points mechanisms used at all five: the design used is now obsolete.

NR began the replacement works for the points after first installing the system on the line to Pembroke Dock, at the Tenby loop, on 7 December 2009 and then making minor alterations in Feb 2010.

In 1987 tragedy struck the line near Llandeilo when the Glanrhyd Bridge collapsed following heavy flooding, and an early morning northbound train plunged into the swollen River Towy, killing four people.

The short tunnel before the former station is the oldest surviving example still in use in Wales (dating from 1839), whilst the freight-only branch along the Amman valley to Gwaun-Cae-Gurwen diverges at the latter.

North of Llandovery the character of the route changes, as it ascends into the Carmarthenshire hills towards the first of the line's two major summits at Sugar Loaf (820 feet (250 m) above sea level) on gradients as steep as 1 in 60.

[11] En route, it passes over the 283-yard (259 m) long Cynghordy viaduct across the Afon Bran valley before crossing the county boundary into Powys through the 1001-yd (915 m) summit tunnel beneath the Black Mountain range.

From Llandrindod, the line climbs steadily once more, skirting the Radnor Forest as it heads for the remote station at Llanbister Road (some 5 miles (8 km) distant from the village it is named after) and another summit near Llangynllo Tunnel, the highest point on the route at 980 feet (299 m) above sea level.

From May 2015 an additional Monday to Friday train pair in each direction was introduced north of Llandrindod and south of Llandovery, ostensibly to improve commuting possibilities, although the consequential changes to existing services substantially lengthened the working day for those travelling to Shrewsbury.