Dr Thomas Stuttaford

Time is on your side. Few couples want to sacrifice everything they have built up in more than 30 years of marriage.

Inevitably, divorce after so long would be an emotional and financial disaster for your family, as well as for the family of your husband’s female friend — if, indeed, he has one. Remember that you are now working on suspicions rather than facts.

You don’t tell us if you have any children. If you have, and you think that just because they are now in their twenties they won’t react badly to a marital break-up, you are mistaken. Step relationships, if it came to that, are always notoriously difficult.

Families, even better than courts, understand that responsibility for even apparently unreasonable behaviour is usually the result of the actions of both partners in a marriage. It is important to understand that there are usually factors that have prompted an erring partner to stray.

You would be less than human if your suspicions were confirmed and you didn’t feel rejected, insecure, jealous, angry and unappreciated.

But you don’t know who you are up against, what to do about it (if anything), and why the affair started.

The depth of your jealousy will depend on your level of insecurity. Once someone becomes obsessively jealous they lose touch with reality, they find it difficult to assess information accurately or dispassionately and may exaggerate the importance of what they, perhaps wrongly, have interpreted as clues of infidelity.

The insecure and jealous usually become self-critical, depressed and self-obsessed. Depression inevitably leads to feelings of guilt but, perhaps paradoxically, people always interpreting family problems in relation to themselves.

My late mother-in-law told me that she was always adept in their early married days at spotting when my father-in-law had been attracted to another woman.

Some women, but not my mother-in-law, might have attempted to freeze out the unwelcome competition. She invited her rival to the family house on every possible occasion: she had her to stay; no lunch or dinner party was complete without her; and my mother-in-law introduced her to every member of her extensive family.

Initially my father-in-law and his prospective amour were delighted but they became increasingly uneasy. Robbed of the illicit excitement and engulfed within the family, the poor woman was overwhelmed and my father- in-law embarrassed.