England started running out of  places to bury people. 
So they would dig up coffins and take the bones to a bone-house, and re-use the grave. When reopening the coffins, one out of 25 coffins were found to have scratch marks on the inside and they realized they had been burying people alive. So they  would tie a string on the wrist of the corpse, lead the string out through the coffin and up through the ground and tie it to a bell. 
Someone would have to sit out in the graveyard all night (the graveyard shift.) to listen for the bell; thus, someone could be, saved by the bell or was considered a ...dead ringer.

i tried burying kev the chauffeur to try this out, but he insisted the string should be tied to the bell at the flying whippet pub.  hence the saying, pulling a pint.

a doctor checked him out once and was shocked to find blood in his alcoholstream.

why am i telling you this?
because history is happening now, all around us, you see.