Alexander Wang's oversized blazer from Browns
Oversized blazers aren't a new trend but I think this is one of the nicest ones I've seen. The grey is a nice change from the ubiquitous black and feels fresher for the summer. They've also gone to the trouble of pre-pushing up the sleeves for you by adding a few pleats to the elbow and cropping the sleeve to mid-wrist.
This kind of proportion looks great with cropped trousers or you can team it with a soft floaty dress to contrast with the tailoring. Oli's lilac dress I picked recently would look great with the jacket which is £560 from Browns.