the way of water

The electrician had a very brief poke at this yesterday and declared that it might be the master water inlet stopcock, which he'd been looking for in order to earth it. Unfortunately, it appears to be made of lead and so had better not be carrying any water, but also heads off south-east, goes through a floor joist then goes upwards and through the floor, terminating in a sawn-off hole just by the skirting on the left, confirmed by half an hour of poking webcams and torches through holes when a phone on a monopod was still too big. The real stopcock is one of two to the left of the washing machine, which at least slides easily in and out after I put it on a sheet of hardboard when it was installed.