The Southern Railway (SR) gave the designations 4Cor, 4Res, 4Buf and 4Gri to the different types of electric multiple unit built to work the route between London Waterloo and Portsmouth Harbour. The 4Cor type units survived long enough in British Rail ownership to be allocated TOPS Class 404. The Cor designation had previously been used for the 6Pul units and was reused by them during World War II when the Pullman car was stored, but this stock was different from the 4Cor units.