Apparently the sky was even more beautiful before I took that shot, but I was stuck in a meeting prior.
I did my best to prevent reflections of the offices lights bouncing off the windows creating flare, but I couldn't eliminate all of it. I realised after posting some of my post processing to fix it is a little OTT, there's an overly dark patch to the right hand side of the photo.
I would have loved a longer lens (I was using a 17mm prime on my Olympus PEN which has a 2x crop so 34mm in 35mm equivalent), as it was I've cropped quite a lot from the top and bottom of this photo. It's also very noisy too.