The message
from Tim S contains these words:

PPS - we are actually doing the 3-phase/63A socket thing at work, for
temporary computer room power when the submain distribution boards are
being worked on. There will indeed be a 3 phase plug feeding a temp
distribution board feeding a load of flying 32A single phase sockets. All
approved and being done by pros... Temporary in this case means 24-48 hours
mind...

At least you're not doing what a firm I worked for did. Portakabin
arrived, couldn't be bothered to wire in properly to the fusebox so for
a "short term" solution they made up an extension lead with a 13A plug
on each end and covered the one in the Portakabin with lots of gaffer
tape once it was plugged in.

This lasted for months.

--
Skipweasel
Pay no attention to that man behind the curtain.