I'm getting increasingly confused, particularly about some of the comments.
If my understanding is correct (maybe not?), but as the OP has recently reminded us, it seems that the armour has been 'cut back' and is now buried under concrete. If that is remotely true then:
(a) there's no point in people going on about 'glanding the SWA properly', since it appears that armour is no longer available to anyone ... and
(b) all of this discussion/argument is therefore about whether or not there is a (theoretical, but unachievable) need to earth some metal armour which happens to be surrounding a cable which is entirely embedded in concrete and which therefore will never be accessible or touchable.
In other word, in the situation the OP finds himself in, I would day that the armour is a total irrelevance.
Kind Regards, John