Very old custom London Underground fluorescent fitting

I'd been meaning to get a picture of one of these for quite a while. In the late 1940's or 1950's I believe a large number of these sleek fittings were installed on the tube network, all running BC fluorescent tubes. Nowadays a number still survive, although sadly all of the ones I've seen recently have been running LED retrofit tubes - I imagine they have gone through several gear/tube type changes over the years however. I'd imagine (fingers crossed) that these will be preserved in future.