 The class was absorbed by British Railways in 1948, and like their N class counterparts were given the power classification 4MT in 1949.Under British Railways ownership, the class was reclassified from 4MT to 4P5FB in 1953; the "B" denoting the brake power rating when used on unfitted (non-vacuum braked) goods trains.The locomotives at first retained their Southern Railway livery, but No.