This is the coolest coat ever! Able to be a long winter coat or zipped off to create a boxy blazer. I saw one exactly like this in Cos yesterday and it was love at first sight (which quickly turned to hate when I saw the price tag). I have seen mountains of gorgeous coats in Charity Shops recently, never for more than a tenner. To DIY this, buy a thrifted coat in a nice wool, decide where you want to be able to zip the coat in half (thinking about the appropriate length for the little half coat), cut off, and a attach zip by sewing both long raw edges to the edge of a heavy duty zip. Voila!
Image: Stockholm Streetstyle