A very very hungry caterpillar

We have a very overgrown ( and full of knotweed) allotment behind our house, which I have repeatedly asked the council if we can take on. Apparently there’s a queue of people waiting so the answer is no. I beg to differ however as there is 6 unissued plots and has been for the three years I’ve lived here. *Sigh*

Anyway the allotment is also full of ivy and bramble which has overgrown into our garden , and that has been somewhat neglected recently. Today I made a start
On the rampant ivy and found loads of these caterpillars... so it’s another identifying job!