If such an alarm was fitted, there would be at least one reference to it. Don't you think it would have been mentioned in relation to the phone call to Jeremy from Ralph by at least one person? And with all Robert and Ann's weird and wonderful theories, neither mention the personal alarm in any of them? There is no evidence that it was there and until, there is, I will remain sceptical. It seems Jeremy also recollection that it was fitted after and as a regular visitor, I think he would know. However, I am still waiting to be 'proven' wrong. 
Caroline, good morning

I hear what you say and I understand your reasoning. My own personal experience of a family who had one installed because one of them and their children were under threat of murder, hardly constitutes concrete proof. All I can say is that once the threat was removed, so too, was the panic button. If magistrates don't get them fitted as a matter of course, what would bve the point of fitting one in an unoccupied house OR a place where there was NO specific threat. For me, this is key. The threat must be serious, real but specific. IMO, it would be useless for A and R to say they were concerned that X MAY try to break in, or Y looks like a shifty character. If that was the case, most of us could have requested one at some time, but if they were so readily distributed their efficacy would be dramatically reduced.
Why would the wider family know of its existance if Nevill had chosen NOT to tell his close family. He had the opportunity to tell BW during the somewhat cryptic conversation he had with her regarding his concerns, but he said nothing. As to why he didn't reach automatically for it that night, I can only suggest that, strictly ethical man that he was, he reasoned that it would be an abuse to use it for any purpose OTHER that that for which it was installed AND as it had always been, family business was sacrosanct.