Investigating a noisy auxiliary belt to find this lodged into the radiator fan housing. It seemed to also be lodged from one of the central pulleys, underneath the tensioner. It pulled out very easily. Wasn't stuck. Most of it was in the pulley/belt area.
Seems it used to be circular though has clearly snapped and mangled. I'm trying to convince myself it popped up from the road but given how high up it was and the under tray in situ I know that's doubtful.
Does anybody know what it is?
No symptoms apart from the remaining rattle and no air con (have ordered new compressor pulley though that sits lower than where I found this object).
Thanks for any replies!