The bee-parasite Sicus ferrugineus (Diptera: Conopidae) on ragwort. I have previously blogged about this rather strange-looking fly back in June, here. As I stated back then, these flies lay their eggs on bumble bees. While I was taking the present photos the subject flew up and momentarily 'touched' a passing bumble bee. I presume that this was an attempt at egg-laying, though I am unable to say whether it was a successful attempt.
Photos taken on Hangingstone, near Guisborough, North Yorkshire, UK, on 2009-08-01.