Cats still not getting along with my other cat 1 year on

As the title says, we have 2 cats, aged 6 and 7, male and female, our 2 cats have always got on fine. We decided to take on another cat, got her from thornberry 1 YEAR ago, neither of my 2 cats have ever got on with the new cat which is female aged 2 years, but I kept reading this should pass and they should eventually get on, well a year later and they are even worse, particularly our torti female, she absolutely hates the new cat, my other cat which is male is not much better with her which is not like him either as he is a really laid back cat with others on our estate. The best way i can describe it is that the torti in particular treats the new cat like an intruder, she chases her out of the garden, sits at the cat flap and doesnt let her in, fights with her whenever she can, its very vicious. The new cat barley comes in, i cant feed them all together, its just getting ridiculous. Sorry to keep referring to the 2 year old one as the new cat, shes not new anymore as a year is a long time but wanted to try and make it clear. Does anyone have any suggestions? The new cat is also now very nervous, which i would like to add she wasnt like when we got her, she cowers whenever she is in the house, its not nice to see. We just want all 3 cats to get on like our other 2 have,. Also all 3 cats have been spayed, neutered. Claire

You need to set up a barrier gate and, on one side, put the established cats, on the other, the new cat. Then feed them, so both sides can see/hear/smell the other as they all eat, but can't physically get at, or fight/intimidate each other.

Also, make sure there's a litter tray available for each cat, plus one extra.

Most of all, go to youtube and watch "my cat from hell"- there's several series of it and the guy is a real expert on cat behavioural issues- several episodes deal directly with cats not getting on, and, he pretty much sorts it out every time.

as suggested try a safety gate/barrier and separate the cats and feed in separate areas so they dont have the chance to fight each other etc

hopefully the fighting will stop if they have there own space,

Thank you for your replies, will certainly look up the videos. Anyone any ideas on why they still wont get along though? I don't see it improving after a year still, although it is strange that when I come downstairs in the morning the torti and new cat are asleep a few feet away from each other on different sofas in the living room, never hear any fighting in the night.

Have you tried the Feliway Diffuser? a lot of people have had great results from using it.

No not tried it, didn't know if it was a bit of a con! Might have to give in and try it, torti is always in a bad mood though so don't know if anything can calm her down that much, I am guessing some cats can just be more stressed than others though