Rishworth Caterpillars (Possibly Cabbage Moths)

Recently I found what I think are 2 Cabbage Moth caterpillars feeding on the garden wild Lesser-Swine Cress. A quick update on the Elephant Hawk Moth and it is sheltering under a half eaten leaf!
The larva has stripped 3 Himalayan Balsam plants since I found it.
Below find an attached picture of one.

                                                     It is alive just wet as it was still munching!

                                                     Is everyone sure it is a Cabbage Moth larva.