The South Western Electricity Board was formed in 1948 as part of the nationalisation of the electricity industry by the Electricity Act 1947. It was an electricity supply and distribution utility serving south western England.
The company was privatised in 1990 and became SWEB Energy. In 1995 SWEB Energy was acquired by the American utility, Southern Company. In 2003 SWEB was sold on to French-owned EDF Energy, who discontinued the SWEB brand name in 2006.
Initials only overprints (x4a) and full name overprints (V4d) used by the utility are common. Much scarcer is style H4d, shown here on SG 465.