On Mar 9, 5:56*pm, wrote:
Was it really necessary to increase the earth conductor size? It was only
needed in some cases where rewireable fuses were used. It may have been more
economical to have outlawed fusewire, requiring cartridge fuses and MCBs to
be used.

It was also with regard to length, even with MCBs.

Plenty of sparks ran 7/029 T&E with 30A fuses due to its current
carrying capacity being higher than 27A FTE-2.5. It is here where the
smaller CPC was distinctly skimpy despite the line & neutral
conductors being plenty beefy enough. Quite a few small kitchens got
30A in 7/029, better installs got much larger (probably as butyl began
to fade as PVC came in).