In article ,
Andrew Gabriel wrote:
ISTR that was pretty standard in most house in the '15A round pin plug '
era...

It was also used for the best part of 20 years for ring mains, too.

Yes -- one of the design aims of the 30A ring circuit was easy
conversion from a 15A radial system (by making the ring start
and end at two existing 15A outlets, converted to 13A of course).
Hence the two schemes used the same cable (and you were allowed
to keep the two 15A fuses at each end of the ring early on too).

But it was also used on new builds which only ever had ring mains until
the arrival of the current 2.5 TW&E - which was part of metrication.

--
*Marathon runners with bad footwear suffer the agony of defeat.*

Dave Plowman London SW 12
RIP Acorn