The house we live in is about 150 years old, and we have been here five
years, during which time I've never tried to turn off the incoming mains
water. Tried this morning, and the handle just spun around on the
shaft, so used a pipe wrench to close the stop cock. Apart from
discovering that the cold water supply in the kitchen comes from the
tank, everything was fine until I tried to turn the water on again.

The stop cock is jammed solid, in the closed position. Any ideas how to
open it again? I have sprayed penetrating oil around the shaft. Would
heating the stop cock with a butane blow lamp possibly help?

The stop cock is brass, and feeds copper pie above. I think the
incoming pipe is probably lead, as it is bulbous where it joins the stop
cock.
--
Graeme