My cheating partner thought I’d forgiven his affair and assumed, at 53, I was too scared to leave. Instead, I got revenge in the most delicious way… and here’s how: KATE MULVEY

If you’ve ever had a partner cheat on you, you’ll know the sickening anguish. The hours of sobbing down the phone to friends. The self-doubt nagging you at 3am.

Why did he cheat on me? Will I be able to trust him again? And the biggie: should I take him back?

While therapists might talk about resolution, restorative growth and the power of forgiveness, my advice is simpler: change the locks and cut up his favourite jacket.

Because an affair isn’t ‘just sex’ or a ‘mistake’; it is a conscious betrayal. When someone cheats, they are making a mockery of you, your shared history and your emotional safety.

And even if you try to forgive them, you never truly can. I should know. I learnt the hard way.

I was bowled over when, then aged 51, I first met Mike, 59, at a friend’s party. Rugged, with a piercing stare and a mop of brown hair, he flirted with me as we discussed art. I was incredibly attracted to him and the relationship progressed quickly.

At first, he was everything I could have dreamed of in a partner.

Yet I was too blind to see the red flags waving my way. The long hours supposedly spent at work. The weird way he started guarding his phone. The evening he donned a grey cashmere jumper and brand-new trousers, just to babysit his niece.

Finally, a year-and-a-half after Mike and I got together, a friend took me for coffee and dropped the bomb: my boyfriend was having an affair with the manager of a restaurant he frequented.

I felt physically sick, time seeming to slow down around me.

That evening, I stormed round to Mike’s flat to confront him. He begged me to forgive him, I was the centre of his world, he said. He would take me away on holiday.

Then he put his head in hands and sighed. He didn’t feel heard. I was always busy. Blah blah blah… and yet I fell for it.

Part of the problem was I struggled with the idea of a fresh start alone. I was 53 and I felt that time was running out.

So we talked and cried until the early hours. He told me about his childhood, how his father would leave him in the car whilst he went drinking in the pub. Apparently this so-called childhood trauma excused his behaviour.

I cradled him in my arms. We even made love that evening. Silly, silly me.

I was reminded of my conundrum over whether to forgive Mike last week, when Norwegian Olympian Sturla Holm Lægreid publicly confessed to cheating on his girlfriend. He begged for forgiveness, calling her the love of his life and pleading for her to take him back.

Thankfully, she does not seem inclined to do so, saying his actions were ‘hard to forgive’. But should she waver in her resolve, let me reiterate: it would be a big mistake.

Because here’s the thing the therapists don’t tell you. Even if you try to take him back, you will lose part of yourself in the process.

While the relationship limped on for a few more months, I soon became a version of myself I hated – the paranoid, jealous harpy. I found myself policing his every move, checking his phone while he was in the shower, demanding to know where he’d been when he came back late in the evenings. If he glanced at a pretty blonde in the street, it felt like a sickening blow to my self-esteem.

It took its toll. I was holding two opposing thoughts in my head: he loves me and wants a future with me. He slept with her and lied to my face without blinking.

The truth is, I wasn’t living with him; I was living with the ghost of who I thought he was – who I hoped he was.

It would always descend into ugly power struggles. He went on the defensive and told me I was insecure and needed therapy. I struggled to sleep, caught in a fog where the truth felt entirely out of reach.

When I told him he’d played me, he replied: ‘Stop it, Kate. I love you.’

But you cannot claim to love someone while simultaneously choosing to betray them. Infidelity is an act of self-interest, not affection.

In the end, I didn’t get over it by ‘working through our issues’. I got over it by kissing another man in front of him.

It was at a gallery opening of a mutual friend we were both attending. I was dressed up to the nines in a slinky dress, high heels, the full works. As we swanned around separately, a handsome photographer I knew vaguely sidled up to me and put his hand round my waist.

‘Wow,’ I thought, followed by ‘why the hell not?’

I saw Mike watching out of the corner of his eye as Mr Photographer pulled me to him and we had a flirty smooch. He even took my number.

’Did you like that?’ I said, mockingly, to Mike afterwards. He was furious.

‘Well, now you know a bit of what I felt,’ I said – and walked out. It felt glorious.

It was my way of saying I’d moved on, that I deserved better. I hope that Lægreid’s girlfriend has realised the same thing. 

• Mike’s name has been changed