It looked like they were trying to mate and while doing so they opened and closed their wings regularly. I was just lucky to get that shot. I witnessed this a number of times.

Today I saw more than 30 Grayling at Cambois, Northumberland.
A couple of dozen were on an old industrial site of crushed brick and concrete, but also saw these on buddlea.

[/album]I was trying to identify this one by taking a photograph with wings closed, when it lifted off as I took the shot. Have I got a Large Heath, which were otherwise about in good numbers at Harwood Forest, Northumberland yesterday.