From a my morning walk a few days ago: conopid fly Conops vesicularis (Diptera: Conopidae). These seem to be quite variable in the color and extent of the dark markings on the thorax and abdomen: in some the markings are black, in others reddish brown; in some they extend less than half-way down the abdomen, in others they go right to the tip. However, the dark triangular markings on the wings, and the relatively long antennae seem characteristic of this species. The reddish form is similiar to, but a bit larger than, Sicus ferrugineus which I saw several times last year. The larvae are parasites of bees nests.
Photo taken in Whiteknights Park, Reading University grounds, Reading, UK, on 2010-05-18.