Thanks for the info Mancat !

I think with my cat and the visiting cat it may be a case of my cat having moved into part of the other cats territory - from what I've read a cats version of territory is very different to a humans!

Well this afternoon the visiting cat came into the garden but Tipsy ran him/her out !! There was a bit of wailing but no fighting.

So I think they will sort it out themselves . I just need to remember that my cat is a cat and not a human !!