"wanderer" wrote in message
...

Butyl rubber was a common insulant within the electricity supply
industry 60 to 70 years ago, used for lead-in cables to properties.
Much has been replaced, although it still turns up in predominantly
rural locations.

Lead sheathed cable is now considered to be unsafe for electrical
installation work, and should be replaced ASAP.

I'd guess that at least third to a half of all the houses in the country
still have lead-sheathed paper or PBJ insulated service cables. The supply
industry doesn't seem to be in any hurry to replace them.

--
Andy