I have just returned from taking Ollie to the Vet this morning.
After getting his booster vaccinations, and a full check-up, the Vet pronounced that there is nothing wrong with him whatsoever. His weight, temperature, and heart are all good, and he has no signs and symptoms of any infection or discernible illness.
My concern about Ollie not eating as much and drinking more water was put down to Ollie’s age, and the fact he has slowed down considerably. Less rigorous exercise means that he is not as hungry, and because it has been unusually cold and we have had the heating on might well make him more thirsty in the house.
It seems I was over-reacting, but I am glad that Ollie has been checked over, and is fine.
Thanks to everyone for your concern about him. That is always appreciated.