Guess which end is the head!

I spotted this nearly 3 inches of caterpillar feasting on a small variety of spurge last night and hoped it would still be there this morning. It is even better larger

The underside view is fascinating and well worth looking at

I have no clue as to whether it will be moth or butterfly but I am gobsmacked by the amount it has eaten in the short while I have been watching.

P.S. this has been identified by ceridwen as a Hyles euphorbiae spurge hawkmoth larva which is actually used as a biological control of the weed leafy spurge. " The white and red spots appear as the caterpillar increases in size, and in a few weeks it becomes a most beautiful object, and so conspicuous as to attract the sea-gulls and terns, which devour them in numbers".