We've had our 6-yr-old cat (neutered male) since he was kitten - he has
always been the most easy-going, placid and affectionate cat you could
hope to come across.  Last December we got a 3-month old kitten (a
female, spayed at 6 months), and not unsurprisingly, the older one was
not at all impressed.  We'd hoped things would settle down, but 4 months
on, it's really no better and I'm wondering what we can do to help the
situation.

Most times when they come within a few feet of each other, the old one
hisses and growls, and quite often will attack the kitten - it's
particularly nasty when he runs across a room and corners her.  She once
had a severe abscess on her nose as a result of one scratch wound.

We put them in separate rooms at night - the older with the catflap as
usual, and the kitten elsewhere with a litter tray.  They are fed
separately as they are on different food and each wants to eat the
other's... bizarrely though, the old cat has no problem at all with the
kitten diving into his food bowl alongside him.

We've definitely made huge efforts to pay lots of attention to the old
cat to try to avoid jealousy, but to no avail.

Just to complete the picture we also have a 6-yr-old spaniel, who gets
on perfectly well with both cats. Go figure!

Is there anything else we can do here to sort this out?

Thanks
David