I've always hated affairs. They ruin lives. My dad cheated on my mum over and over again and every time she forgave him. I swore I'd never take a person back if they cheated on me. I also swore I'd never have an affair. That promise with myself I kept.

Me and Kathy were strained and I realised that I was more in love with Liv than I was with her. After 6 years being partners we were so close. I noticed I felt more for her than I probably should when Alex was shot. She lost her best friend that day. I was there to comfort her every step of the way. We become closer than ever then. She confided in me stuff I never would have believed.

She had been in a relationship with Alex for 11 months prior to her being shot. She told me how much she loved her and how she felt like a part of her had also died that night with her girlfriend. I became her rock. I couldn't tell her I was in love with her right after she'd lost her girlfriend so I just decided to be her friend.

Kathy started to be on at me all the time about how much I was working and how I was shutting her out. I started spending more and more time with Liv. We'd be together all day at work then I'd go back to hers and we'd order a takeaway. I'd go home late all the time until eventually we separated.

I had nowhere to go at first so Liv offered me her spare room until I could get sorted out. I was wary at first but she was insistent. I moved in with her and started looking for a new place.

We both soon decided that we liked the company so I put looking for a new place on hold. We'd been living together 7 months when I noticed our relationship had changed. She no longer bothered to put lounge pants on and walked round in shorts and a vest. We sat closer together when we were watching the TV or a film and she started to put her head in my lap when she was tired. I realised I was falling further and further in love with her and I couldn't keep it in any longer. That's when I got my divorce. I no longer had anything in my way and I could finally make my move.

I wanted to get it right. I decided one night that I'd cook for her for a change. It was great she loved it and we talked for ages. We decided to watch a film and so I went through her DVD collection. I let her choose the film and she chose some sappy romance film called PS I love you. I was shocked to find that I really enjoyed the film. About 20 minutes in like clockwork her head found its way into my lap. I don't know what possessed me to do it but I started to run my fingers through her hair. I didn't even notice I was doing it until she started to silently sob.

When I heard her I immediately asked what was wrong. Bad move as soon as I said this she sat up and started to sob harder into my shoulder. When she eventually calmed down she told me that that was something which Alex used to do and she hadn't felt it for a very long time. I apologised for making her upset but she told me that the reason she was crying was because of something else.

She said she was crying because she had started to develop feelings for someone else and so she felt like she was betraying her. I told her that Alex would be ok with her moving on and that she should close off her heart she deserved more than that and Alex wouldn't want her to be alone. That's when it first happened. She leant up and kissed me. I was so shocked that I didn't respond at first and she pulled away before I had chance to. She looked so embarrassed and started apologising. I told her to stop apologising and kissed her back. I'd never felt anything more euphoric. Her lips were so soft. That night I fell a little deeper.

A month later and we was in a full relationship. Everything was going great we had just told the squad and they accepted it. Still no one knew about liv and Alex. 3 days later we had to arrest Alex's "killer". That night Liv didn't sleep. She had nightmare after nightmare of Alex being shot. I couldn't even imagine what she was going through but I promised I'd be by her side all the way.

The next day Alex came back. She was here to sort out the mess we got ourselves into. She never died she went into the witness protection programme. She was still in danger so we had to protect her. Liv stayed with her that night. It was the first night we had been apart for a month.

We won the case and we was all going to celebrate when we found that it was still too dangerous for Alex and she went back into wpp. That night Liv was devastated. She cried for hours. I held while she let it all out. What she then told me made my heart shatter. She told me that she had cheated. She told me everything about how seeing Alex had surface old feelings and that the blonde had looked so broken and lost and how she just wanted her to feel safe. After her breakdown I forgave her. That was the first time I broke my rule.

Soon after we was back to normal. 2 months after Alex had gone back Liv told me she loved me. She said it first. I was waiting for the right time but she said it first. It was the best feeling in the world. I felt like I'd waited 7 years for her to say it. She told me how she'd wanted to tell me for ages but didn't know how I'd respond. We talked all night that night about how we felt towards one another. 3 days later I asked her to marry me. She said yes.

We got married later that year and went on a honeymoon to Paris. Our first child was born at the beginning of this year. She's called Lola. She is just like Liv.

Lola was a month old when we got the news that Alex was coming back for good. I had mixed emotions about this. Liv on the other hand seemed distant. Alex had been back 3 weeks when I started to notice the change. We talked less; made love less even kissed less. I also noticed she hardly ever went for a warrant herself. She always sent Fin her partner if he wasn't too busy.

One afternoon I was out investigating a lead, when I got back it was 4:55 (nearly end of shift) so I just gathered my stuff and went to see if Liv was ready to go home. Fin told me she was in the interrogation room having a "discussion" with Alex which usually meant an argument. I expected to walk into a blazing row but when I walked in they were both crying and holding each other.

As soon as they noticed me they looked up but didn't quite break apart. That night when we got home Liv told me how she and Alex talked it all out and how they are going to go back to being friends. This was the happiest I'd seen Liv since she got the news that Alex was back.

After this every Tuesday Liv and Alex would go for lunch. I was absolutely fine with this. We would also have Alex over for tea a couple of nights a week. She was great with Lola and even offered to look after her when I and Liv wanted to go out.

One day after chasing a lead I got back to the precinct with the intention of grabbing lunch with Liv but she wasn't there when I got back. The guys told me she was over at Alex's office so I made my way over. I just walked in without knocking and what I saw broke my heart.

My wife had her tongue down the ADA's throat while our ADA had her hand down my wife's jeans. I didn't need a PhD to work out what was going on. I left before either had a chance to see me. This was the second time I broke my promise.

Later on I rang Liv to see if she wanted to grab a beer with the guys. She didn't come but told me to have fun. I tried to forget all about what I'd saw but it was playing in the back of my mind the whole time. I left around 10 but came home to an empty house. I found a note telling me how this just wasn't working for her and that she's sorry for hurting me but her heart always truly belonged to Alex. I guess I have always known that though.

I've always hated affaires, they destroy people's lives. Who knew I would let one destroy mine.