Please ID another odd wire!

This one is totally of academic interest but it's got me puzzled...
I've found an ancient, thin cable tacked to the outside wall of my 1913 house. It's three twisted strands of uninsulated copper wire (total OD about 1-2mm), which emerges from the concrete ground adjacent to the house wall, then runs up the wall for about 1.2m where it is stapled to a wooden windowsill, and has been chopped off, and the whole become buried in layers of paint over the years. My guess is the cable originally may have gone through a hole in the sill and into the house?
This all happens close to the front door, near where all the services (elec/phone)enter the house.
What would the cable have been for? Some form of earth maybe?
Thanks David
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Could it have been an earth wire for a crystal-set-type radio (or wireless, as it would have been called at the time!)?
Roger
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