Cat Invasion

Hi, my gentle little 15 year old female cat is being terrorised by a local tom, who has been circling the house and tonight actually came inside (the door was ajar while we were cooking) before being chased away. I have an infrared catflap but don't have the lock in use because the clicking freaks my cat out. As it is, she often 'camps' just inside the back door and is unsettled by this other cat and its increasing encroachment into her space.

What should I do?

Thanks

I'd keep her inside or only allow her outside when you can supervise. Who does this other cat belong to? If no one, maybe you can catch him and take him to the shelter.