I must admit, I can't get passed that going through a cavity wall (certainly a challenge for the cat to get through) was not the best but 'only' option!? Aren't there any doors (preferably with glass panels) nearby, that could have been used?
Which brings me to the next query, do you have any windows nearby that the cat could look out of - to keep watch for the unwanted tom-cat!?
My cat (when not sleeping) loves to stare out of the upstairs bedroom window, downstairs will do the same with the French-doors, too much of a diva to go through the kitchen back-door cat-flap during the day, but at least does during the night - helped by movement sensor lights just outside.