BR Class 404

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

Due to the inter-unit corridor connection and the connection with Portsmouth, they were known as 'Nelsons'.