Lone surviving G.E.C Z5590

I spotted this lone surviving GEC Z5590 on a proper classic concrete column still standing on one of the access roads that run through RAF Cosford.
It has obviously been burning an 80 or 125w MBF lamp as the UV has had it's way with the polycarbonate bowl over the last 50 or 60 years!
You can't see it but that bowl should be clear with a glass refractor ring around the lamp!
All the others have been replaced by modern columns and lanterns but this one seems to have been forgotten.
At some stage it has been fitted with a two-part Royce Thompson P42 photocell. I bet it had a time clock originally!
If it still works then I think the output would be quite poor...