I noticed these clouds from my cottage late morning today. They actually got a mention on the weather forecast just before the 1:00 pm news on BBC Radio 4 having formed this morning over parts of Devon and Cornwall. Apparently they are technically called Cirrus uncinus clouds formed at about 10km high in temperatures of -40 to -50 degrees C where moisture droplets get very quickly super-cooled. It's unfortunate that I had no better foreground than my cottage and its immediate surrounds.
The lens used was a Voigtlander 12mm Ultra Wide-Heliar