Single core and earth cable, and the related product single core insulated and sheathed without earth, still used today but applications are limited.

The material with a single insulated core and a bare earth wire was for the live or phase conductor and had a red or brown insulated conductor and a bare earth wire. For the neutral single core insulated and sheathed cable without an earth wire was used with a black or blue insulated conductor.

Often used for lighting circuits when a larger than normal number of wires needed. Example a chandelier with three separately switched groups of lamps, use a three core and earth cable for the three switched lives and the CPC. For the common neutral use a single core insulated and sheathed cable with a blue or black core.

Also used within control panels when it was desired to continue the SAME conductors, without jointing outside of the control panel, thereby rendering single insulated panel wire inappropriate.

Sometimes used for bell or signaling circuits if they used mains voltage rather than the more usual ELV. Or for bell circuits at ELV  if something more robust and "better" than bell wire was wanted.

I have used the single core and earth cable for house wiring at 12 or 24 volts with the bare wire as the neutral, not really correct, but use of the intended earth wire as a neutral would not worry me if it was for the earthed side of an ELV system.

Single core and earth cable, and the related product single core insulated and sheathed without earth, still used today but applications are limited.

The material with a single insulated core and a bare earth wire was for the live or phase conductor and had a red or brown insulated conductor and a bare earth wire. For the neutral single core insulated and sheathed cable without an earth wire was used with a black or blue insulated conductor.

Often used for lighting circuits when a larger than normal number of wires needed. Example a chandelier with three separately switched groups of lamps, use a three core and earth cable for the three switched lives and the CPC. For the common neutral use a single core insulated and sheathed cable with a blue or black core.

Also used within control panels when it was desired to continue the SAME conductors, without jointing outside of the control panel, thereby rendering single insulated panel wire inappropriate.

Sometimes used for bell or signaling circuits if they used mains voltage rather than the more usual ELV. Or for bell circuits at ELV  if something more robust and "better" than bell wire was wanted.

I have used the single core and earth cable for house wiring at 12 or 24 volts with the bare wire as the neutral, not really correct, but use of the intended earth wire as a neutral would not worry me if it was for the earthed side of an ELV system.