I returned to the wood last evening, just as it was getting dark.  I was armed with my Bat detector, a pencil and a pad.  It was a little eerie in the half light and the calls from a nerby fox added to the atmosphere.  The calling went on and on, and seemed close so after a short while I left the quarry and walked towrds the calling fox hoping to get closer. As is usual with truly wild animals,  as soon as I got reasonably near to the fox, now just over the brow of a hill, it stopped calling  and slipped away silently. The bat detector did not pick up any bats while I was in the field which was interesting, but back a the quarry I picked up some really interesting echo locations, they were low, around 20-20 KHz, slow clicks followed by much louder double slaps. Very interesting. I am quite confident that I was listening to a  Noctule Bat  (Nyctalus noctula), one of the UK's largest species and as big as a Starling. Tonight in my own garden, I used the bat detector again to listen to a Soprano Pipistrelle that was zooming around my house. Great to have one again this year.