Picture-Wing Fly

A grey picture-wing fly of species Platystoma seminationis (Diptera: Platystomatidae).  It seems that there is only one other species of Platystomatidae found in the UK, and that is Rivellia syngenesiae which looks nothing like the above, so I feel pretty confident in the above identification.  The Platystomatidae are more important in other parts of the world, indeed some of the most bizarre-looking known flies belong to this family (see here and here, for instance).

Photo taken in the field below Chazey Wood, near Caversham, UK, on 2011-04-25.