Unusual Sky at Eggardon, Dorset

Eggardon Hill is one of the highest places in Dorset, it is the site of a Roman hill fort, and there is an annual kite festival held there, and today was the day
There was certainly enough wind for kites, I went early to get some blips of kites, before the weather broke into the gale and heavy rain that was forecast.
Being a bit of a sky watcher, I was delighted to see this cloud formation, the likes of which I have never seen before, so this is my Blip for today, not a kite picture, I hope you like it.