How to conveniently check lengthy multicore cables

The number of fairly complex multicore cables in the home and the workshop is steadily increasing. The workshop PC brings with it a printer, keyboard, mouse and monitor, possibly a network connection and probably a modem line. All of these items require a dedicated connector and a multicore cable to connect it all together.

Buying commercially-made leads can be expensive, and even then, you may not be able to get exactly what you require and have to manufacture your own; with the attendant doubt that all is wired, and wired correctly! Testing these leads can be confusing, especially if there are several to make up of the same type.