These small black flies appear each year in my garden for about 2-3 weeks.
They have very dark grey wings, almost black.
They are about 5-7mm long and spend almost all day inactive sitting on the wall of the house, they never come indoors.
As soon as you get within a few inches of them they fly off and land about 6 inches away, very reluctant to move far.
Last shot was taken with ringflash so shows slightly different detail.
Would be grateful if anyone knows anything about these.