Anyways, I went outside to smoke and there he was, waiting by the door for me. I decided to let him into the back garden whilst I smoke - wtf was I thinking!!!

He looked around the garden, then hopped onto the wooden fence that separates my garden from my neighbours and started scratching. All this time, I had a pouch of food for him to tempt him back in as he hasnt eaten yet.
Then he jumped up on top of my neighbours shed and starts making this weird noise - like an wolf howling! When I jumped up to see what he was doing I noticed there was another cat there. KTW was still howling but I could see his whole body trembling, as he edged closer and closer - in slow motion. I didnt want to think the worst but then he got really close to the cat and then they started fighting
So annoyed at myself. I eventually had to climb over the wall to go and get him, as I could see that KTW was going back for more (the other cat started it but KTW wanted to finish it!)
I never want to to take him outside again as Ive seen that cat many times (idk if its stray or owned by one of my neighbours) but I just wanted to get this off my chest. I cant believe I did that, let alone what I just witnessed.
He is back inside now and Ive given him some food, but I burst into tears apologising to him for being so stupid for letting him out
