The first members of the XR class were rebuilt in from first and second series X class locomotives between 2002 and 2004, with more powerful rebuilt engines cascaded from the G class, larger radiators, and a new cab to provide better driver visibility.[1] They were not reclassed and renumbered as the XR class until 2004. The second group of three locomotives were built from new, entering service from late 2005. They differ from the earlier units as 'elephant ears' noise deflectors are fitted to the radiators.