From two years ago: a rather over-exposed photo of a Subclytia rotundiventris (Diptera: Tachindae). I include this imperfect photo because it nicely shows the shape and colour of the head. Here is a somewhat better photo of the back:
Some more photos of this fly can be found here.
Photos taken in Whiteknights park, Reading University grounds, Reading, UK, on 2009-06-04.