Written by why do double insulated appliances not need an earth wire?
class 2 appliances are commonly known as double-insulated equipment, the live parts are encapsulated in basic and supplementary insulation (double), or one layer of reinforced insulation
An electrical appliance which is double insulated (which should be marked with the symbol to the left) does not have an earth wire fitted. The appliance is designed in such a way that the electrical parts can never come into contact with the outer casing of the device. Common double insulated appliances are hair dryers, radios, modern garden tools and cassette players.
A wet double insulated appliance is exceptionally dangerous – water is a good conductor of electricity and will easily reach the live electrical components within the case. Any human user touching the casing will then receive an electric shock.
For this reason, do not operate a mains radio, hairdryer or double insulated appliance in any wet area – especially a bathroom
If you need to wire a new plug to such an appliance just follow the instructions for “how to wire a plug” and just ignore the section about connecting the Earth wire.