Herman Miller Embody. Got it from 2ndhnd.com. Had been refinished in red fabric, has the white skeleton.
It was listed for £550, but I got a 5% discount and free shipping. Which is about half of the RRP. I had been through a few "gamery" chairs and none of them were really doing me any favours, so once I switched my Humanscale Freedom Headrest I had kinda decided that any chair I bought from now on would be a proper office chair. The Humanscale had gel arms, and whilst this is a nice upgrade they tend to split because they are a bit too soft. That's usually where all of my chairs go. So I got this when I moved into the new place.