A cat is coming in the house everyday.. help!

[Supermagicsmile]

We have one cat who is mainly an indoor cat. He goes out for the toilet but not for long as he is terrified of a local cat let's call him 'Bob' who hisses at him and traps him under our car etc.
Bob has recently started coming in through the cat flap. It's now a daily thing and he will eat our cat's food, licking the bowl clean which our cat never does.
We have tried blocking the cat flap but Bob has pushed everything we have put there out of the way including cardboard boxes, a plastic box, a plastic box filled with cushions and then a plastic box filled with cushions with a chair wedged against it!

How do we stop him coming in? Our cat won't wear a collar so an electric cat flap isn't possible.

Has anyone got any suggestions that we could try? (We are not sure where Bob comes from so can't locate his owners!)

[PersianCatLady]

Can you not lock the cat flap?

[Supermagicsmile]

We can but our cat needs to get in and out twice a day to use the toilet!

[Gerbil17]

Get a paper collar from your local vets with your phone number wrote on asking for the owners to call you.

Cats are stubborn and determined little fuckers

[SteelyPip]

How about a chipped cat flap? Then only your cat can use it. Works a treat for us.

[reetgood]

Microchip Cat flap. It’s pricy but is totally worth it for our timid Cat. No need for a collar, only the correct cat can enter or exit!

[SteelyPip]

Great Minds! @reetgood

[reetgood]

@steelypip :) I couldn’t believe I was spending so much on a cat flap when I got it, but it’s so worth it. Have had the cat being chased in, with it slamming shut in the face of his pursuer. Works brilliantly (although trying to get home to use it/register his chip was slightly farcical)

[Oops4]

Sureflap microchip cat flap, best money you'll spend

[mumworkingfromhome]

Call any local groups that help in catching and taking the animals. If you let this happen, it will become a nuisance.