Lewm, not quite correct. Additional observations were
I was explaining to the gentleman why touching the SME armtube did not induce hum - anodising.
Provided additional options for insulation on the arm for aesthetics - get a painted one or use heatshrink rather than plastic.
Rubber shoes/mat I cant see anywhere - a bit off the wall, but I have seen this work.
I refrained from suggestions like removing his pacemaker or turning the cellphone off.
I have also seen hum issues or rf issues where there have been poor solder joints in the cable loom between the cartridge phono input sockets that whilst hum is not present, touching the arm induces it - not a ground loop issue, more of an antenna effect.