Blooming hard commute in this morning, due to a combination of a headwind and low sun in my eyes. There were times I was cycling with one hand on the handlebars and the other shading my eyes, in order to be able to see more than 10 yards ahead. As a result, my average speed was one of the slowest for going in, at 15.5mph (I'm usually between 16.2 and 16.8 on the way in, between 15.3 and 15.7 on the way home.
But on the way home, the wind was still the same, so with a nice tail wind, and the sun high enough to be no issue, I had the fastest ride home I've ever had, at 16.5mph. I think that is the first time ever I've been faster on the way home than the way in (there is 50m more climbing on the way home, and one climb which is significantly harder and slower than anything on the way in, plus the usual wind direction is tailwind on the way in, headwind home).