On 26 August 2020 a freight train carrying diesel fuel and gas oil in tank wagons derailed at Morlais Junction, Llangennech, Carmarthenshire, Wales.

The clean-up operation was described by Natural Resources Wales as the most challenging since the Sea Empress oil spill in 1996.

At about 23:15 BST (22:15 UTC), the 6A11 21:52 Robeston Sidings (Milford Haven) – Theale freight train derailed and caught fire at Morlais Junction, near Llangennech, Carmarthenshire.

[1][2][3] The train, operated by DB Cargo, comprised a Class 60 locomotive 60062 Stainless Pioneer and 25 tank wagons,[3] each carrying up to 75 tonnes of diesel and gas oil.

[10] Once BTP had established that the derailment was accidental, they passed control to the Office of Rail and Road (ORR).

[11] Dyfed-Powys Police set up an 800-metre (870 yd) radius exclusion zone, and about 300 local residents were evacuated from their homes.

[16] On 6 September, it was claimed by Member of the Senedd and Deputy Transport Minister Lee Waters that the railway could be closed until December 2020.

Local cockle and other shellfish picking was suspended following the spill on advice from the Food Standards Agency.

[20] Work to remove 12,000 cubic metres (16,000 cu yd) of contaminated soil from the site began in December.

The leading axle of the front bogie had seized, causing a 230 mm (9-inch) flat spot to develop on one of the wheels, along with a false flange.

[26] On 30 October 2017, the brakes on a wagon of a tanker train from Robeston had seized causing a severe flat spot, before the axle became free again.

Track between Carmarthen Junction and the Llangyfelach Tunnel, a distance of 72.2 kilometres (44.9 mi), was severely damaged.

[27] On 5 November, the RAIB released an Urgent Safety Advice notice relating to the maintenance of wagons used primarily for the carriage of dangerous goods.