The very angry caterpillar

This caterpillar interrupted supper yesterday, and posed an interesting question. Is it a successful example of Darwinism, because it had learned to use our hosepipe as a motorway to cross the jungle (for something its size) of our lawn? Or is it unsuccessful, because I saw it as a result? I am trying to identify it; not as simple as you might expect from something so distinctively marked. Waring, Townend & Co have only a limited number of photographs of caterpillars, so I shall have to roam the internet when time permits. If you have children/grandchildren, or are childlike yourself, now is the best time to watch out for caterpillars. You will often come across 'woolly bears', which are great travellers. They can give some people a mild skin rash, though not me. I also remember finding Drinker moth caterpillars as a child in Herefordshire. They give themselves away by climbing stalks of field grass in the early morning to quaff on the dew. The caterpillar wasn't very angry, as per my headline, but it did roll up in a defensive ball.