Older cat behaviour

[FlyMeToDunoon]

My 15 year old neutered tom has started turning his nose up at Iams [I know, and I mean to stop buying it when this bag is finished]. He has always eaten dried food.
I have tried him with Sheba wet food which he has wolfed [tigered?] down. Teeth seem fine.
He sits outside all day in all weathers, sleeping on wet ground sometimes. When he does come in he eats and goes out again. In the evening he will occassionally sit on my knee for maybe half an hour before he's out again. I don't know if he comes in at night I just hope he does.
His behaviour has always been nervy but it is getting worse and worse.
Is this normal in older cats?

They do get a bit picky about food when they get older, I think they can't taste it as well, or get bored with a certain type, and are enthused by a change. My neutered old male preferred gravy to jelly and if there were any peas included in the sachet they were licked clean and left in the dish!

It seems odd that he seems so keen to be out so much, most of them prefer to stay in more. Mine used to like a final patrol of the garden and around the front, sniffing all the scent messages from other cats late at night and would then come in. He also preferred to use the litter tray as he felt safer. This started when the local bully cat pounced on him in his own garden, luckily we saw it happen and were able to chase it off, but it frightened him and he was cautious after that.

Maybe your cat feels he has to defend his territory outdoors, or is something in the home upsetting him and he's staying out of the way?

Thank you for replying.
My cat seems even more sensitive to noise and disturbance. He tends to appear more in the evenings whe the DCs are in bed.
Our garden is very enclosed so I think he feels fairly secure there and hates a litter tray.
I guess I will just have to monitor his health and see how he gets on over the winter.