Thanks all for the messages - well maybe no thanks for the unhelpful messages... We are in the process of swapping our normal "low-tech" cat flap over for a microchip one. (Any recommendations for handymen who can do this?) But this cat is devious and, even if it weren't, having windows and back doors open in summer is pretty reasonable, even for EDF'ers. My goal of the post was for the owners of this bully-boy to ideally keep him in at night, consider neutering (if not done already) and feed him a bit more so he stops his scrounging. So if he is yours please do help out - sleep deprivation is not a good look for me.