Why Tribal destroyers could show black staining near the bridge and funnels

What caused the black staining seen near the bridge and funnels in photographs of Tribal-class destroyers?

Fuel-oil handling in that area was one likely source, and nearby shipboard waste areas could also leave marks.

Photographs sometimes show dark staining on Tribal destroyers just aft of the bridge and around the funnels. Fuel oil taken aboard in that part of the ship could leave some of those marks. Nearby areas used for shipboard waste could also contribute to the grime. No single cause should be assigned to every black patch in a service photograph.