What happened to the cat flap?

I noticed last night (while making a cup of tea) that it was really cold in the kitchen; especially around my ankles! I couldn't work out the problem at first until I looked down and saw that the cat flap was missing. It took me a while to figure out what had happened and many theories went through my mind. The first was that someone had been trying to break in and had tried to get in by removing the cat flap, sticking their hand through and somehow unlocking the door! I soon realised that this was unlikely as the door was still locked and nothing was missing. I was confused as I couldn't see the cat flap anywhere. However, after a look outside with the powerful torch I found it half-way up the garden, the door broken beyond repair. Later I noticed that Mandi had a few cuts and scratches and I figured that the most likely explanation was that one of the neighbourhood cats had come in for food, Mandi had tried to fight him off and they had both gone crashing through the cat flap in a hurry. I have ordered a new cat flap but in the meantime it's still cold in the kitchen! Ian says that if he catches any other cats in the kitchen he will take them outside and pee on their heads and that should stop them coming back!