Thanks David, Phil & Chris!
The Dragon Fly in Flight (DIF) was the single frame from over 20 where the head of the DIF and the auto focus point coincided. On the other frames, I had either a sharp tail, or wing, or the DIF was half way out of the frame or just an empty frame! These really are “chance” shots when they come off!
I think that these creatures can somehow sense when you are focusing on them; they seem to hover for a tantalising second or two, but as soon as you acquire them in the viewfinder, they instantly side slip out of view.
Cheers
Dennis