How Type G works
The upper earth pin is part of the safety arrangement and helps open shutters in compliant sockets. UK plugs are normally fused, so the chosen adapter must be appropriate for the appliance and connection.
Travelling from continental Europe
Type C and Type F plugs do not fit Type G directly. A properly designed adapter is required. Because the UK supply is 230 V, many European devices are electrically compatible, but the label still decides.
Protective earth
A two-pin Europlug remains unearthed by design. A Schuko appliance that relies on earth needs an adapter with continuous earth to the Type G plug.