A rapid burst of pupupupupupupu! I opened the window..... pupupupupupupu* again..... but now almost repeated continuously......
(* I couldn't even begin to spell what it sounds like!!!)
Eventually I got onto it, bearing down on me over the middle of the pool....
Then in a flash, overhead and high - gone - heading North.....
I started to walk back to see Martin (probably at the same time he decided to walk to me!) We met in the middle and exchanged a simultaneous "Did you see that"? The seven whistler strikes again!