0 7 , ▁following ▁the ▁failure ▁of ▁his ▁I 1 ▁class , ▁Douglas ▁Ear le ▁Marsh ▁sought ▁to ▁rem edy ▁some ▁of ▁the ▁fault s ▁with ▁a ▁new ▁design ▁of ▁ 4 - 4 - 2 T ▁with ▁a ▁longer ▁wheel base , ▁larger ▁bo iler ▁and ▁detailed ▁changes ▁to ▁the ▁front ▁end . ▁In ▁the ▁original ▁order , ▁five ▁of ▁the ▁locomot ives ▁would ▁incorpor ate ▁a ▁super he ated ▁bo iler , ▁to ▁be ▁supplied ▁by ▁the ▁North ▁British ▁Lo comot ive ▁Company , ▁and ▁the ▁remainder ▁traditional ▁s atur ated ▁steam ▁bo ilers ▁from ▁Bright on ▁Works . ▁In ▁the ▁event , ▁the ▁super he ated ▁bo ilers ▁were ▁delayed ▁in ▁construction ▁and ▁so ▁all ▁ten ▁I 2 ▁locomot ives ▁had ▁traditional ▁bo ilers . ▁ ▁I 4 ▁Class ▁ ▁When ▁the ▁super he ated ▁bo ilers ▁eventually ▁arrived ▁they ▁were ▁used ▁for ▁five ▁further ▁locomot ives ▁of ▁the ▁same ▁design ▁as ▁the ▁I 2 , ▁but ▁these ▁were ▁class ified ▁as ▁I 4 . ▁ ▁Unfortunately ▁the ▁neither ▁the ▁I 2 ▁nor ▁I 4 ▁class ▁addressed ▁the ▁fundamental ▁problems ▁with ▁the ▁I 1 ▁class , ▁which ▁was ▁a ▁fire box ▁that ▁was ▁far ▁too ▁small . ▁As ▁a ▁result , ▁the ▁two ▁classes ▁had ▁relatively ▁short ▁lives ▁working ▁light ly ▁loaded ▁secondary ▁services , ▁and ▁the ▁Str oud ley ▁D 1 ▁class , ▁and ▁Bill inton ▁D 1 ▁class , ▁which ▁they ▁had ▁been ▁designed ▁to ▁replace , ▁continued ▁working . ▁ ▁Number ing ▁ ▁L B & SC