Paul has always been a quiet, reserved man with a few close friends, but none who live locally. His life outside of work has been devoted to making Maggie happy.

Maggie started to become worried when Paul was staying up at night watching the street outside the house for men in cars. He also became more suspicious about her movements, questioning her on return from shopping with regard to her whereabouts.

Paul is becoming lower in mood through his belief that his wife is being unfaithful, despite her protestations to the contrary. Maggie is feeling frustrated and impotent at her inability to reassure Paul that there is nothing wrong.

There are probably very few of us secure enough in ourselves and our relationships not to worry occasionally about infidelity and betrayal – they are real enough factors in many people’s lives. Some people have to live with near obsessional jealousy in themselves or in their partner.

However, Paul’s behaviour is odd and out of character. Although dementia can produce behaviour like Paul’s, it is jumping to conclusions to decide that it is the product of dementia, though it can certainly be a symptom or an accompaniment to symptoms.

On the one hand it might be the product of relatively easily treatable mental health problems such as depression or anxiety, which can produce paranoid symptoms or even a late-onset psychotic disorder. On the other, it might be the result of the kind of stress that makes us all behave oddly from time to time.

It would be very difficult to tell initially, however over time the behaviour is likely to settle, disappear altogether or harden into a regular pattern of symptoms of one kind or another. Medical monitoring would be vital in any of these cases, in case of escalation.