I believe this to be the species identified in the title as there are several similar species. Although its has a similar metallic green to some of our Greenbottle flies, it actually belongs to a family of flies called Dolichopodidae, known as the long-legged flies for obvious reasons.
I noticed it for the first time earlier this year around my garden pond, and this is the sort of habitat they enjoy, damp and moist. The adult as seen here are predacious, and they feed on soft-bodied arthropods and can help keep pests down such as aphids. Maybe that’s why I keep finding it around my roses as well as my pond.
They are generally seen May to July, and, besides my garden, can be found in wet grassland, hedgerows and woodland margins. Fairly common and widespread in England and Wales.
Please click on the images for a larger more detailed view.
Rear garden, Staffordshire, England. June 2017.