@cstross Let's hope anyone trying to follow this (how?) will also manage to get hold of a plug like that, because at least then they'll be entirely unable to insert it.

Then again have had an installer show up once and so utterly terrify me with his blatant disregard for safety (wiring things up very obviously incorrectly without turing the circuit off did not endear me to him) that I took over because I'm certain I was more competent, I'm sure people will find a way...