Ice falling from a cloudless sky

Yesterday morning, at around seven, I was walking along the Thames when I stopped to look out along the river. After a few seconds a snowball-sized piece of ice fell several metres in front of me, onto the Thames' riverbanks. There were no clouds in the sky and the nearest building was so far back from where I was that I doubted someone could've thrown it such that it landed at such a steep angle.

I should've gone and taken a closer look at it. As it was, I was glad to have seen it at all. Now I have my own one-in-a-billion story that I can use when people are talking about amazing coincidences.