On 26 August 2020 a freight train carrying diesel fuel and gas oil in tank wagons derailed at Morlais Junction, Llangennech, Carmarthenshire, Wales. Some of the derailed wagons caught fire, leading to an evacuation of people living nearby. There was widespread contamination from the spilled fuel. The clean-up operation was described by Natural Resources Wales as the most challenging since the Sea Empress oil spill in 1996. The accident was caused by defective brakes on a wagon causing an axle to seize, which in turn caused deformation of the track under the train as it travelled over a set of points. The Heart of Wales Line was closed for seven months as a result of the derailment. Accident 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. The train, operated by DB Cargo, comprised a Class 60 locomotive 60062 Stainless Pioneer and 25 tank wagons, each carrying up to 75 tonnes of diesel and gas oil. The third to twelfth wagons derailed, spilling of fuel. The train was travelling at at the time of the derailment. There were no injuries reported amongst the two train crew. Following the accident, the locomotive and first two wagons stopped from the burning wreckage. The locomotive was uncoupled from the wagons and moved to safety. Class 66 locomotive 66004 moved the wagons at the tail of the train away from the scene of the fire. A large number of emergency services and local authority personnel attended the scene. The British Transport Police, Dyfed-Powys Police, Carmarthenshire County Council, Mid and West Wales Fire and Rescue Service and Natural Resources Wales (NRW) all sent personnel. Fourteen fire appliances, a foam tender and a high pressure pump attended the fire, which was expected to burn for several days. By the evening of 27 August, six of the appliances had been withdrawn. The fire was extinguished at 08:30 on 28 August, having burnt for 33 hours. Control of the site was then handed over to the British Transport Police (BTP) and Network Rail (NR). Once BTP had established that the derailment was accidental, they passed control to the Office of Rail and Road (ORR). Dyfed-Powys Police set up an radius exclusion zone, and about 300 local residents were evacuated from their homes. They were later allowed to return. The railway