Do Anglepoise lamps need an earth connection or are they double insulated?

Anglepoise lamps manufactured from the mid 1990’s have been designed and tested as Class II or double insulated electrical appliances, which means they are designed in such a way that they do not require a safety connection to electrical earth (ground).

These lamps will be marked with the double square symbol -  

If you have an older or vintage lamp and it is not marked with this symbol then it is possible that it will require an earth connection, if in doubt check with a qualified electrician.

The basic legal requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is achieved by having two layers of insulating material surrounding live parts or by using reinforced insulation. Hence the outer material can be metal as the risk of becoming live is negligible (many household products are similar).

References:

Directive 2006/95/EC - Harmonisation of the laws of Member States relating to electrical equipment designed for use within certain voltage limits; IEC 61140: Protection against electric shock — Common aspects for installation and equipment. 2001; BS 2754 : 1976 (1999): Memorandum. Construction of electrical equipment for protection against electric shock.