Description 37421 Colas Rail Stored by EWS at Motherwell in March 2005 and sold for preservation at the Pontypool & Blaenavon Railway in 2009, No. 37421 was one of four Class 37s that was purchased by Colas Rail in 2013 for a return to the main line, along with Nos. 37116, 37175 and 37219. While the latter pair debuted for their new owner in the middle of 2014, it would be another year before No. 37421 would re-enter traffic along with BR green-liveried former Harry Needle Class 37/0 No. 37057/D6757, just in time to assist on the newly acquired Network Rail infrastructure monitoring contract. For the next four years, the Colas Class 37/4 was a solid performer on various test formations, until called to South Wales in May 2019 to provide power for Cardiff-Rhymney line commuter turns along with hired-in Nos. 37025 and 37418. This followed a fallow few months when the locomotive was under repair and eventually returned after a bogie swap with No. 37175. The Rhymney workings ended in March 2020 and it was back to test train work, mixed in with NR saloon duties with No. 975025 Caroline and the odd infrastructure duty. Cosmetically, towards the end of that same year it swapped its Colas˜hard hat logos for new diamond stickers, although it has stubbornly retained its unique arrangement of single lamp irons on different sides of the locomotive at each end. Despite the increasing number of Colas HST power cars on the NR services, No. 37421 is still a regular atop PLPR (Plain Line Pattern Recognition) and UTU (Ultrasonic Testing Unit) formations and is expected to remain a key component of the operators fleet for several years to come.
