The key requirements in bringing a new cat into your home where another cat or cats are already well established are patience and a gradual approach. First, allow the newcomer to explore the house without coming into any contact with the feline inhabitants. The reason for this is that behaviourists have found that where a cat is on unfamiliar territory and meets a strange cat which is familiar with it, the former is far more interested in first investigating its surroundings than in checking out the other animal. Territory is of supreme importance to cats.

Next, put the new cat in a room alone with its own food and water bowls, litter tray and bed. Begin feeding the new cat and the other cats on either side of the door, putting their dishes near, but not too close, to the door. Gradually, over a day or two, move the dishes closer to the door.

Now, open the door a crack, just sufficiently for the cats to be able to see one another while they feed, and wedge it. Also, exchange the bedding of the newcomer and the residents so that they become familiar with each other's scent. Some experts actually recommend spraying both lots of bedding with one of the cat scent pheromones, such as Feliway, that are now available. Once the newcomer is eating and using its litter tray regularly, allow it out from time to time to explore the house again, still without meeting the other cats face to face.

Finally, you can open the door wide for a while so that the cats can mix. Do it gradually, extending the contact time more and more as things settle down. There may well be some moderate displays of aggression and fear with some growling, hissing and spitting at first, but unless they are severe, these almost always tend to diminish steadily. If you see either cat becoming distinctly aggressive or frightened, separate them, not by charging in but by throwing a large towel over each of them and carting them off so that they can reconsider things. You will then need to begin the introduction process once again. Make sure you have a litter box for each cat plus one extra. During the 'getting to know you' period, which can last weeks, it is best to keep the cats separated when you go out.

Throughout the process of introduction, it is vital that you continually boost the confidence of the resident cat. It should receive more attention, more fussing over, than the new arrival. Of the two cats, it is the one to feel affronted, and it will be on the lookout for any sign that your affections have been transferred to this Johnny-come-lately. Of course you must make friends yourself with the newcomer, play with it, stroke it and talk to it, but in the initial period you should do this only when the resident cat is not present. Whenever you are with the cats, keep talking, always quietly in an upbeat, encouraging tone of voice, never shouting or scolding.

This familiarization by separation technique, of introducing animal strangers to one another is essentially the same as that used in zoos and safari parks for tigers. In their case there is more visual contact, as the two animals are on each side of a gated mesh barrier. There is of course no question of human beings going in with them, let alone holding them on laps. With tigers, the two individuals get to know one another well, but without bodily contact, over a much longer introductory period of at least one year. When, at last, it is considered time to open the gate and let them mix, it is always an event of high tension for the zoo staff, even though for months the animals may have behaved impeccably towards one another.

A tranquillizing dart rifle is loaded and ready, just in case, although most tiger introductions pass off without trouble, but it is not very uncommon, as the two big cats at last come face to face with no weld-mesh between them, for one suddenly to pounce and, within the twinkling of an eye, deliver the classical, lethal neck bite. No time for tranquillizing darts then. The cause of the tragedy, once again, is probably territorial.