it is surprising how many you used to see like that, in fact YEB are there used to be lots of similar kind of earth clamps on incoming PILC but more like a buckle, same principle as as "Temby" type earth clamp though , usually had a short small diameter earthwire to the MET that probably only had the current carrying capacity of a piece of wet string, yep there were lots like that around 2,5 to 4.0 diameter earthwire on a clamp.
Mind you, years ago, all services gas, water etc were either lead or copper, miles of it all connected like a truly massive great earth rod/plate and lots of cast iron too, if you lost your electrical earth you you still well earthed in practice from all that pipework and everybody else no PME/TNCS back then it was all TNS (or out in the sticks might be TT) an earth was an earth was an earth back in those days in the towns and cities