Origins of UK standard 13Amp plug

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

I have been asked if I know anything about the origins of the standard 13Amp
plug used in the UK.  Surely one of you UK coilers knows this (or where to
find out)?  (Although, I have to confess, I have no idea about the origins
of the standard 15Amp plug used in the US... but, at least I know where to
start tracking it down...)

Thanks in advance...
Jim