What happens in a relationship when one person has an affair? How does it happen? What does it feel like? Can a couple overcome it? This couple says you can.
The first time Pete was unfaithful to his wife was when she was pregnant with their first child.
Having just started a new job as a policeman, he wanted to show he was "one of the boys" - which he says motivated him to approach some women on a night out.
"From then on, any chance that I had an opportunity to stay away from home, I would be looking for an opportunity to have a casual sexual encounter," Pete explained in the documentary 'Me and My Affair'.
"Once you've done it once then you just go and do it again. The fact that I got away with it, the fact that I had to lie about it was just an integral part of the activity that I was involved in."
Pete got away with his constant infidelity for 17 years.
For that time, Pete's wife Nikki still had complete faith in her husband.
"He was working really long hours and he would phone me at the time that I expected him home, and he'd say that he'd got to work late, 'Kiss the kids goodnight for me, I'll see them in the morning' [He'd say], and for quite a while I didn't resent that at all," Nikki explained.
"He always used to say to me how important marriage was to him and I believed him."
It wasn't until an affair with a colleague meant he might lose his job that Pete's lies began to unravel. After finally admitting to being unfaithful, Nikki couldn't look at Pete. While at first she thought there was only one indiscretion, the extent of Pete's infidelity eventually emerged.
"I agreed to meet with him. I can remember, actually, we walked the streets at about 2 o'clock in the morning and he showed me this list, and the list had 23 names on it," Nikki described.
"[There were] dates and there were descriptions of where they'd met, how many times they'd had sex, how long it had gone on for, if it was anything more than a one night stand.
"I looked at the dates and realised it spanned our entire marriage.
"It's just like my heart had been ripped open. My world had just imploded."
Pete describes this moment as the lowest point in his life. But this wasn't the end of their marriage.
Instead of kicking Pete out, Nikki forgave him. She believed that, at the end of the day, the love they had really was "unconditional".
"I just had had this moment of clarity. This was not about me and my failings, this was all about Pete and his pain, he needs help," she said. "It was like all of a sudden I realised the true meaning of unconditional love in a marriage."