Hawkmoth Caterpillar

Taken on an old derelict construction site now a thriving meadow where all manner of invertebrates flourish, i happened across this rather large Hawkmoth Caterpillar (I think)..it seemed happy enough posing as it chomped on the surrounding vegetation.

I have been told that this species favors a specific plant, namely Epilobium or "Willowherb" which is what the Caterpillar in my picture is enjoying


*EDIT* It's actually an Elephant hawk moth Caterpillar.