Hi , I'm James DVM MRCVS and would like to help you with your problem
The big question is what is going on with Norman that is causing him to drink a lot and eat un traditional food
If considering Normans age , there are several conditions which come int mind .
1. is he diabetic
2. does he suffer from renal (kidney) disease
3. Is he suffering for an thyroid disease (being over active) - though no common in cats of his age
4. maybe his adrenal glands are over active due to a tumor - resulting in the presenting symptoms
and the list goes on and on
The bigger question is if you wish to investigate it .
I personally think that its worth while investigating by mild means - meaning performing a one off blood test and urine test could give your vet much information about Norman's condition and even come up with a diagnosis that might be treated .
To that aim you should make an appointment with you vet to be seen early next week . But for now you should make sure Norman is drinking all he wants (his body is demanding it ) , supply him with boiled chicken as food and try and stay clear of anything else, like ham , cheese and such salty processed foods
You can give him some spring water tuna as well.
But again , most importantly , WATER AS MUCH AS HE WANTS :)
I hope I have helped you.
If you wish to discus the matter further , just let me know .
all the best