I have been finding these insects in my London flat for the last week. Several of them every day. They fly I believe. they are about a 1cm long if that.

Post's pictures

IMG_3424.jpg, 453.29 kb, 2448 x 3264

IMG_8645 (1).jpg, 729.52 kb, 3264 x 2448

They look like cockroaches some of which can fly short distances.

Paul has mailed us to say:

"These are not cockroaches. They are True bugs of the insect order Hemiptera. In the second picture, you can see the Cris-cross wing pattern typical of this order of
insects. The second picture is fuzzy, but I think they are Boxelder bugs."

I agree these are not cockroaches or indeed anything to worry about too much.