Didn't have time for a photo, but an official looking "Do not leave horse manure here" sign on a roadside electrical cabinet with Severn Trent Water branding and contact details.
I assume there's a story to that oddly-specific instruction. Presumably involving somebody (who? why???) using the adjoining concrete platform as a convenient (?) place to store manure, to the frustration of some long-suffering engineers who required access to the water-related infrastructure beneath.
ETA:
Found it. No sign, but possible evidence of poo on the concrete? It's a sewage pumping station, ironically.