After six months Jess moved into our flat. “You don’t mind do you mate?” Jez asked. “It’s only temporary.” I didn’t mind at all, I craved her carefree company. But their relationship was fiery. And when Jez’s new job took him away more, Jess and I spent more time alone together in the flat. Those evenings with her, sharing late night chats about life over Chinese takeaways and wine, would be some of the happiest of my life. I’d dare to stretch out an arm across the back of her seat. Occasionally, she’d rest her head on my shoulder and I’d want to punch the air with joy. “Rich*,” she said to me one, quite drunk time, naked underneath Jez’s T-shirt and looking me straight in the eye. “Do you ever think we should be together?”

Christ, did I. More than anything. But when she moved her hands along my jeans towards my inner thigh I entirely freaked out. I just couldn’t do it. I muttered something about Jez being my best mate and went to bed, frustrated and loathing myself for not grabbing my chance. And that was that. A few months later, when Jess unexpectedly fell pregnant, I moved into my own pad.

But we always had a connection. When she was struggling as a new mum it was me she leant on, me who held her sobbing in my arms one night. I was made godfather, and then best man at their wedding the next year. I took my nice new girlfriend, Claire*, to their wedding, and I delivered a gushing speech.

After a furious row on their honeymoon, Jess messaged: “I think I’ve made a mistake, can we talk when I’m home?” I never replied. What was the point? Instead I focused on Claire, lovely Claire, who was a newly qualified teacher and of whom my parents approved.

Jess and I shared only one real heart to heart after that, when I came to babysit and Jez had rang to say he was stuck in the office and would I keep Jess company instead as she seemed depressed.

Despite her date night dress and make-up, Jess looked shattered. We drank rosé in the garden and she confided that she was miserable. I held her. Remembering how right she felt in my arms. “You know I’ve always loved you,” she said into my chest. I didn’t say all the things I should have – why did she marry Jez? Why didn’t she tell me before? Instead, I squeezed her hard, inhaling the smell of her hair and replied: “And I’ve always loved you,” I said.

We both welled up. “In a different life, eh?” I croaked, pathetically. As strange as it sounds, that moment sustained me for years. The fact we’d both shed a tear was proof that it meant something. My infatuation wasn’t all in my head.

Life carried on. Jess and Jez had another child. I married Claire in 2006. Stable, kind, safe. I did not choose Jez as my best man. I encouraged our friendship to drift. I’d find myself both longing and dreading the monthly couple get-togethers that became part of our lives over the years. When Claire and I had a son I was so proud, I honestly thought I was over Jess for good.

But all it took was one shared glance, a precious few moments alone stacking a dishwasher together after a supper party, and I was obsessed for the rest of the week. Then five years ago, when Jez confided in me that his marriage was in trouble, it played with my mind and I started drinking too much. What if Jess became free? But what about Claire and my son? Alone at night downing Scotch I’d find myself resenting life. I found Claire increasingly irritating, purely for not being someone else. When she accused me of being cold, she was right. I ended up in therapy where (finally) after 17 odd years I said the words out loud: “I’m in love with my best friend’s wife and I married the wrong woman.” I felt like some t*** in a Richard Curtis film but it was a release too.

Therapy did help me give me some perspective. I realised I had a good life, a loyal wife, an amazing son. The therapist drilled deep into whether I was prepared to risk everything for a woman I was “infatuated” (his words) with, who might not – in reality – want me. Would I burn my 30-year friendship with Jez and all our shared mates and history? I realised that I would not.

I’d had many times where I could have declared the depths of my feelings to Jess and I’d not acted upon them. I’d allowed myself to be burdened by my quiet heartache. The therapist also said that feeling like you married the wrong person is more common than people think. (That cheered me up actually.) He reminded me that feelings, even intense ones, were transient. Like everything in life.

Why am I sharing this now? It’s a good question. I think it’s because I’m turning 50 this year, and instead of feeling like a loser, too cowardly to act or confess, I needed to get this off my chest. To acknowledge my feelings were intense but real, to man up finally and ultimately move on. The fact I’ve stopped thinking whether her feelings for me have now passed perhaps means that – at long last – mine have changed too?

Jez is still with Jess. He’s already planning his early retirement. Meanwhile Claire constantly scours Rightmove for second homes by the coast. Some days I feel like I’m drowning, and at times when I’ve felt particularly sorry for myself I’ve tried to embrace that line in one of Tennyson’s poems: “Tis better to have loved and lost than never to have loved at all.” But when you’re grieving a love that you never really had, I’m frankly not sure the heartbreak is worth it.

As told to Susanna Galton

Names and identities have been changed