I'm not so sure. If this was wired 40 years ago, connecting it to any nearby earthy object would in many cases have been considered ok. And any nearby earthy object is effectively a relatively high impedance earth, one that we cant assume will blow the fuse quickly, if at all.
40 years is a lot of time for bodgers to do their work.Even when told, novices generally still dont appreciate the problem enough to make them safe imho.
NT