Leaf muncher

I'm not sure what sort of moth this caterpillar will eventually become*.  I don't think it's a butterfly caterpillar (although I'd be the first to admit that I'm no expert on caterpillar identification).  I've checked my Wild Guides butterfly field guide (Newland, Still, Swash and Tomlinson - highly recommended), and it certainly doesn't look like any of the butterfly caterpillars that they record. 

I found it on the leaves of the pond irises, where It was busy doing some serious damage.  It's sort of amazing that such a small creature can eat so much.

If it had been less windy I might have had a go at trying to focus stack the wee beastie, but in today's blowy conditions that was always going to be a complete non-starter.  So instead I've gone for the head on portrait shot, so that you can see some of the head and mouth parts detail.

There's a flash version as the extra.

* Addendum - I think Incredibish is right with his suggestion (see the first comment below)