Sawfly larvae devouring a dog rose in a park in Bristol. There were several of them and they totally stripped a whole branch over a few days.
No interactions present.
Definitely a sawfly, I expect someone will know which species.
I thought they would.
Many thanks to all of you it seems to be either Arge pagana or Arge ochropus
Lat/Lng: 51.4681, -2.5676
OS grid ref: ST606745