9 ▁August ▁ 1 9 7 9 . ▁Based ▁at ▁W im ble don ▁Park ▁dep ot , ▁they ▁soon ▁became ▁problem atic ▁due ▁to ▁their ▁non - standard ▁dimensions ▁and ▁bra ke ▁problems ▁caused ▁by ▁leaf ▁fall . ▁Once ▁a ▁new ▁build ▁of ▁Class ▁ 4 5 5 ▁EM Us ▁were ▁complete , ▁the ▁Class ▁ 5 0 8 s ▁were ▁slowly ▁sent ▁to ▁their ▁originally ▁intended ▁home ▁on ▁the ▁Mer sey ra il ▁network . ▁Driver ▁training ▁began ▁at ▁Kirk dale ▁on ▁ 1 7 ▁February ▁ 1 9 8 2 , ▁and ▁the ▁first ▁Class ▁ 5 0 8 ▁began ▁service ▁on ▁the ▁Northern ▁Line ▁the ▁following ▁month . ▁The ▁first ▁Wir ral ▁Line ▁service ▁comm enced ▁on ▁ 8 ▁June ▁ 1 9 8 4 , ▁and ▁the ▁Class ▁ 5 0 8 s ▁had ▁completely ▁disp la ced ▁the ▁Class ▁ 5 0 3 ▁fleet ▁by ▁the ▁end ▁of ▁March ▁ 1 9 8 5 . ▁The ▁fleet ▁was ▁then ▁working ▁in ▁parallel ▁with ▁the ▁already ▁well - est ab lished ▁fleet ▁of ▁Class ▁ 5 0 7 ▁EM Us ▁across ▁the ▁River ▁Mer sey , ▁which ▁had ▁been ▁working ▁on ▁Mer se ys ide ▁since ▁ 1 9 7 8 . ▁ ▁Del iver ed ▁to ▁the ▁Southern ▁Region ▁as ▁four - car ▁sets ▁number ed ▁ 5 0 8 ▁ 0 0 1 – 0 4 3 , ▁all ▁of ▁the ▁sets ▁were ▁reduced ▁to ▁three ▁cars ▁for ▁Mer se ys ide ▁operation ▁by ▁the ▁removal