The UK's type G plug: heavy, fused, and used well beyond Britain

The British type G plug is distinctive worldwide for its size and its built-in fuse, a safety feature required by BS 1363 that most other plug standards do not have. Thanks to the former British Empire and Commonwealth, type G is also the standard in Ireland, Malta, Cyprus, Singapore, Hong Kong, and Malaysia, among others, so a single UK travel adapter covers a surprisingly large part of the world.

Travelling within Europe from the UK still needs an adapter

Even though most of continental Europe runs on the same 230V/50Hz supply as the UK, the plug shape is different (type C, E, or F rather than G), so a UK traveller visiting France, Germany, Spain, or Portugal still needs a plug adapter, just not a voltage converter, since the electrical characteristics match.