of a bodyside window and the addition of a ballast weight to give extra 'pulling power' when hauling heavy freight trains, such as the metals trains in South Wales. Again, like the 37/5s, there were two batches completed; from phase 1 and phase 2 Class 37/0 locos. The batch numbered 37701 upwards (curtailed at 37719) were from phase 1 build locos and have the flush front ends and nose-mounted horns, whilst the batch numbered from 37899 downwards (curtailed at 37 883) were rebuilds from phase 2 locos, having the central headcode box (plated over) and roof-mounted horns. A further batch was created; locos numbered 37796–37803 had a different type of electrical equipment fitted (from Brush), as part of a trial, and differ from the other locos in the subclass internally. In British Rail use the sub-class were particularly common in South Wales on heavy coal and metals work. They were particularly adept at working coal trains up and down the short but steeply graded branch lines around Swansea and Cardiff, to collieries such as Tower Colliery, Coedbach and Cwmbargoed. They operated merry-go-round trains of 32-ton HAA air-braked hoppers, usually numbering 32 wagons, between collieries, washeries, open cast mines and disposal points to power stations such as Aberthaw and occasionally further afield. Their use on Metals Sector trains, usually from Llanwern, Port Talbot or English metal works such as Scunthorpe, saw them hauling very heavy trains between docks, works and purchasers in Britain. Indeed, the use of three Class 37/0 locomotives on Llanwern-Port Talbot Docks steel trains (the heaviest on the British rail network at was soon abandoned when Class 56s became available, requiring only two locomotives. Cardiff had a large allocation of 37/7s, some waiting on standby, ready for a call from the mills requiring more wagons to handle any extra traffic. Eventually this work was taken over by Class 56s and Class 60s. This Metals traffic would also become the domain of the sub-class 37/9, which to all intents and purposes was a 37/7 but with a different prime mover. When EWS introduced its 250 Class 66s, from 1998, many of the sub-class were put into store. Some have since been involved in construction work in France and Spain building new high-speed lines. A total of 15 were sent to Spain and an additional two were sent to Italy. Most subsequently returned to the UK, although a handful were