DOH!!!!!! 
Oh, my. Technical director of my company I waz.
Anyway, thanks chaps. Dashed to other room with me slice of toast still in my mouth. Yep, it's indeed that way around. Must get some paint to mark plugs for simple people. Huh, that brings to the fore another 60 year old memory.
I had a boss in the 50's who used to paint spots on the knobs on the tellies so little old ladies would know where to set them. At one house, he pressed the paint tin lid down with his foot, and left a row of circles across her carpet.
You had proper training in those days. C&G practical in Regent St. Parked all day outside BBC house. It was Sunday, but still, a very different world.