Yeah I do feel mean stopping him from looking out if he likes it. It will mean we can never open the window though as we're on the first floor!
I have taken a picture to give you an idea of the height / setup:
What do you think? We were worried because of the radiator being underneath. I have a feeling if he's up there and sees a person, dog or cat then he will start barking as he barks even if he hears a noise outside. Also the windowsill isn't the deepest..