Karate in the Park

Once a year a large group of karate exponents comes to Blackheath for the weekend.
Several groups are scattered across the park and some in the adjacent hall.  
This usually coincides with heavy Blackheath mist and the scene is quite surreal, but when I dropped by the mist had lifted.  
They are always completely engrossed in listening to their teachers and oblivious to anyone with a camera.