....but more importantly did he PAT test it?
Seen plenty of electrical innards in my day that looked fine but were in fact an accident waiting to happen...
Back in the day when working at Marconi's on some digital telephony stuff - the digital repeaters that were required every 1km or so to recover and re-time the digital signal - System-X so 64kHz, I was working with their dev group in Writtle Rd and I discovered a filter part of the cct was quite sensitive to the environment...
Back in the day it was commonplace to wire up a prototype across a 2m+ wide workbench - you can solder freehand- right??
...and lo, i discovered that the cover of Marconi issued A4 notebooks were marginally conductive, maybe 150 KΩ per inch and the part of the cct my notebook was under was a high impedance filter and yes the presence of the book affected the results....