Is this a conupid fly? I've previously had odd singles in my Warwick garden but have seen several this year. With no proboscis visible, if it is a Conops it should be Leopoldius but which one, the slender antenae, banded legs and solid black tail are puzzling me. Am I on the right lines please?
Your photos are very good quality, and when I saw that the insect has four wings I knew it can't be a fly (order Diptera = 'two wings'). That's why I didn't even try to compare your photos with images of Conops or other similar dipterans. To me it looks more like these ichneumonids (with four wings) such as Ichneumon xanthorius. Notice the narrow waist of ichneumons, and the difference between the antennae.
Ichneumonids are difficult to ID, and I'm no expert. Your specimen looks like I. xanthorius to me, but I'm not sure at all.