I see it a lot where the SWA isn’t serving as a protective conductor which I know it must still be earthed at one end due to being an exposed conductive part. My question is if multiple SWAs are all earthed at the supply end and meet again at a bit of equipment if we then connect all the SWAs together locally is this still classed as earthing even though they are already earthed at the supply? 
Graham I am not really disagreeing with you, but there is only one very special condition where the armour of SWA should not be connected at both ends and be part of the CPC. This is where it is desired to separate two differing Earthing systems. Everywhere else there is no reason at all not to terminate the armour with the correct brass gland, and make the SWA part of or all the CPC. In answer to the OP the answer to his question is YES. Why there is a reluctance to use the armour as a CPC is simply a case of misunderstood or bad practice. John Peckham wrote an advice paper a few years ago, pointing out that the armour has sufficient cross section to use as the ONLY CPC up to 95mm if I remember correctly, although in many cases an additional G/Y is installed where it is unnecessary. As SWA always has all the current carrying conductors in the same magnetic loop, heating is not a problem.
In the case of this TT isolation for outbuildings, the armour is electrically disconnected, but even you assume that the sheath prevents touching of two independent Earthing systems! My preferred way of separation would be to use a plastic box, a brass gland as usual, but simply not connect the banjo, and ensure that the boot cannot be removed with some self amalgamating tape, thus meeting all the requirements in one go.I would also add a simple warning label pointing out the separation is at the box.
I can feel the need for a new GN, on installation practice for the tricky cases and slightly unusual cables etc. to go with the OSG, it might be quite popular. I have noticed that may electricians not familiar with SWA fit the wrong sized glands, and that makes proper termination difficult as the armour is fanned out far too much and has to be overlong. BW25 gland on 2.5 SWA being common, it should be a BW20S (small one!).
Graham I am not really disagreeing with you, but there is only one very special condition where the armour of SWA should not be connected at both ends and be part of the CPC. This is where it is desired to separate two differing Earthing systems. Everywhere else there is no reason at all not to terminate the armour with the correct brass gland, and make the SWA part of or all the CPC. In answer to the OP the answer to his question is YES. Why there is a reluctance to use the armour as a CPC is simply a case of misunderstood or bad practice. John Peckham wrote an advice paper a few years ago, pointing out that the armour has sufficient cross section to use as the ONLY CPC up to 95mm if I remember correctly, although in many cases an additional G/Y is installed where it is unnecessary. As SWA always has all the current carrying conductors in the same magnetic loop, heating is not a problem.
In the case of this TT isolation for outbuildings, the armour is electrically disconnected, but even you assume that the sheath prevents touching of two independent Earthing systems! My preferred way of separation would be to use a plastic box, a brass gland as usual, but simply not connect the banjo, and ensure that the boot cannot be removed with some self amalgamating tape, thus meeting all the requirements in one go.I would also add a simple warning label pointing out the separation is at the box.
I can feel the need for a new GN, on installation practice for the tricky cases and slightly unusual cables etc. to go with the OSG, it might be quite popular. I have noticed that may electricians not familiar with SWA fit the wrong sized glands, and that makes proper termination difficult as the armour is fanned out far too much and has to be overlong. BW25 gland on 2.5 SWA being common, it should be a BW20S (small one!).
Everywhere else there is no reason at all not to terminate the armour with the correct brass gland, and make the SWA part of or all the CPC.
Except for single-core armoured cables where "bonding" the remote ends causes problems. Regulation 523.201.
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