It's an interesting take the issue, Barney.
But what does a "simple PAT" actually entail?
1) Protective earth resistance
2) Insulation resistance
Sounds kind of familiar!
What current does the PAT guys shove down the earth conductor?
Whilst I take your point about the legalities of the situation, I doubt that a smart lawyer would be swayed by the argument (unfortunately).
The clue is "medical equipment". Which, as we all know only too well, has a whole box of safety standards all of its own. Which is just how it should be, in my opinion.
Perhaps (with all this talk of PE, testing currents and the like) you're forgetting, what for me is the more interesting point, namely:- leakage current(s)!
If I was on "Desert Island Discs", and could take only one test with me, it would have to be
this one:-
Enclosure leakage. If that one shows less than *100 µA with the earth both open (1) circuit and then closed (2), then all must be well.
1) Represents the "worse case" (or Risk Current) that could flow through someone grabbing hold of the kit when the earth is faulty (missing).
2) If less than (1) - as it should be, and if you can actually measure it - proves that there is an "earth".
*
The limit is 500 µA with the earth lifted, of course.
