A very busy caterpillar

Moving fast along the pavement (me, I have 30 minutes for lunch and had to get to the Post Office) I came across this caterpillar on a mission. He was heading towards an overgrown front garden at speed but i've no idea where it'd come from.

I also don't know what type of caterpillar he is, an evening of books and googling ahead unless someone can put me out of my misery?