I think the cats are communicating. Got my li'l guy (a Bombay) a toy with lots of catnip buried deep inside and he plays with it a few times a day, then the neighbour's Savannah cat turns up and has a run at it, she's basically been visiting every 3-4hrs like clockwork now, head pops round the door, looks at me with shame in her eyes, then heads straight for her fix. Few days later, another neighbour's cat, then today another (they're all clean and friendly).
Might have to 'nip' this in the bud.`
They're each showing up every few hours, coming in through the cat flap, getting strung out on the floor for 20 mins, then leaving.
Turning into the neighbourhood feline drug dealer.