 As with the C class, it was also occasionally pressed into mainline passenger service on key intercity routes, particularly during Christmas and Easter peak times.By 1943, X class locomotives were each averaging per annum.The X class, in common with all broad gauge VR steam locomotives built from 1907 onwards, underwent design modifications to the smokebox draughting and blastpipe dimensions referred to as 'Modified Front End', as well as other improvements such as the fitting of smoke deflectors, Automatic Staff Exchange apparatus and cross-compound air compressors.