A few years back, a friend got a registered sparky in to rewire his recently aquired French house. The previous owners had been Brits and had 'done it up'
themselves. Under the mistaken impression that every circuit required a separate spur, [the Brit Ring Main is illegal here], they had run vast looms of 2.5mm2 flat twin and earth, for everything, in all directions beneath the new sheetrock and in the roofspace, under the floors, you name it. When I say vast, I mean 4 inch plus diameter bundles! In one loom there was a 6mm2 cable intended, I presume, for a never installed range [?]. As twin and earth is also illegal here, the whole lot was scrapped, but most of it is still hiding in there somewhere!
The idiots had also sawed the complete top section out of an 18C oak staircase, which I copied from the lower case and rebuilt in ammonia fumed oak. Nice little earner, 7 days in Bordeaux with me plates up!