The Southern Railway ( SR ) gave the designation 2Hal to the electric multiple units built during the late 1930s to work long-distance semi-fast services on the newly electrified lines from London to Maidstone and Gillingham ( Kent ) . The Southern Railway ( SR ) gave the designation 2-HAL to the electric multiple units built during the late 1930s to work long-distance semi-fast services on the newly electrified lines from London to Maidstone and Gillingham ( Kent ) .