One of the most important manufacturers of ceramic insulators was Bullers.
Based in Milton, Stoke-on-Trent, this company manufactured both small insulators for scientific equipment, radio transmitters, electric trams and the London underground and telegraph equipment and huge insulators used in the developing UK electrical distribution network and which were always seen hanging from pylons.
Other companies amalgamated with Bullers to form the Allied Insulators group.
Phils ceramic story about insulators reminded me that we found one during our excavations at Cnoc an Rath, Bute in 2011. I hadn't really tried to give the item a context until now...