Wow! A guy stopped us as we were walking down Cowley road, asking if we'd ever seen anything like this before. Surprisingly he wasn't a nutter and this was in the sky. You can see the Dunns' flag in the corner. I tweaked the contrast a little in this.
After some research I've found out what this was - a circumzenithal arc. Very rare thing to see apparently. See: en.wikipedia.org/wiki/Circumzenithal_arc
