What is this?

Today is the last Grandad Summer School for a couple of weeks as the students are having periods away camping. I also will be glad of the break. For our last session we are having a "What is this competition?", so I have been wandering around this afternoon with my camera taking various images. Some are more difficult than others (I think.) I have chosen this as I like it as an image.
Another hot day, possibly the last. Enjoyed playing duets with Bill online this morning. We are finding a sonata by Handel particularly challenging.