I admired my sis-in-law and 15 years on I’m still paying for it

DEAR DEIDRE: Every day is one more round of arguing because my wife caught me gazing at her sister 15 years ago when we were on holiday. I’ve never been allowed to forget it.

I’m a guy of 45 and my wife is 42. Her sister is 40.

At the time we were in Benidorm with her sister and her boyfriend. My wife was pregnant with our son.

During the first afternoon at the resort, my sister-in-law came down to the pool dressed in a bikini top and thong bikini bottoms. She looked incredible.

My wife clocked me looking at her and we had the biggest argument ever that night.

After that, whether she’s asking me about how she looks in a new dress or if she’s had her hair done and wants my approval, she’ll say, “I bet you’d love this on my sister”, or “My hair isn’t as nice as my sister’s, but what do you think?”

She can’t resist having a little dig and it causes us to row even now. I love my wife. I want a peaceful life. How can I prove to her that I’m not interested in her sister? I want to be a better husband.

DEIDRE SAYS: You’re being honourable saying you want to be better. But your wife’s argument goes back to that intense jealousy she felt and she never got over.

Find a moment to tell her that you don’t want to argue over the same old thing which then escalates into a big bust-up.

Instead, suggest you work through this residual jealousy with a relationship counsellor. Contact Tavistock Relationships (tavistockrelationships.org, tel: 020 7380 1975) who have reputable therapists.

Ask that once you have worked this through that she finally lets this age-old argument go – for both your sakes.

My support pack called Relationship MOT explains how you can both be kinder to one another.