As I remember, all the cables we used at N-V came from a manufacturer in the Bristol area whose "factory" was a bunch of hen cabins on an old chicken farm. He had developed a way of impregnating both the stranded-steel operating cable and the inner lining of the outer cable with Teflon.You could tie a knot in to outer shesath and pull it as tight as you could and it didn't affect the force needed to pull the inner cable.
I remember driving our company Transit van down to his place to pick up batches of cables. It might be that we only used them on the AJS moto-cross team bikes, as I don't remember picking up production quantities but maybe 30 or so each time.