If he was mine David, as a first step, I would take him to the vet, especially in view of his age, to have a check up and make sure there is nothing wrong with him. If the vet gives him the all clear I would look to see if any other cats are getting into your home and scent marking which would explain your cat's behaviour. Feliway, a cat calming spray might be useful to spray round the area. I used this when my cat, when she was 18 years old, started peeing on my bed. It worked. Anyway, good luck with him, whatever you decide.