Spot on again Jim, that could be the final missing item that that I have been looking for all this time to finally and positively identify potential bivvie anglers....your priceless nugget of information could end a very long search for me mate.
The initial clue I had worked out a while back....that was the friggin great bivvie sat on the bank behind them. However, armed with your ingenious method of identifying these deviants, I need only wait for the angler to fall asleep on his bed chair...then nip along, and a quick search of his bivvie will either reveal a "Jenny said koi" thing you mentioned, or it won't. Great work Jim, I think we can safely say we are well on the way to nailing these simple minded miscreants.
Cheers, Dave.