"Fit for field duties but only in Unit HQ or rear areas."
Tim Huxley mentioned in his book that the PES classification was
finetuned down to let some previously-graded as combat unfit to
pass muster as combat-vocationable, but who will be attached to the
HQ or rear echelon - eg. HQ Signaller, Camp Medic, etc. - rather
than to join the line troops. It supposedly freed up half of the
affected 7,500 cases or something to become operational soldiers,
albeit with reduced IPPT liability.
I think it's the Pes C1L2 grading which serves this
purpose.