Should I tell his fiance he cheated

@Hopelessnaive Do NOT tell her. You've admitted you're only considering doing so to be spiteful - to hurt him - do you want to devastate her when she's done nothing to you? And how exactly do you think this would play out at work once your colleagues find out? You're the OW (albeit unwittingly) so your reputation will not emerge unscathed. Don't do it - you don't need the drama.

I'd usually stay keep out of it but she's about to marry this scumbag. If she buys a house with him becomes fully financially entangled has his kids etc and the he does it again or she finds out in a few years time she will be in a far far worse position. Tell her so she can decide fully informed if she wants to marry him.

Actually if you do decide to find another job you could slip it into the exit interview (I’d also offer to send the evidence to HR). What he did was bordering on predatory when he was your mentor.

Tell her. Send her everything.

Though once a cheat, always a cheat. If they stay together he’ll find someone else to cheat with. Probably the next new girl that joins the company.

i think you should tell her. I was the wife in this position - my ex was the guy you’re describing. He worked his way through several colleagues from receptionists to one of the other senior partners. At the time I had no idea anything was wrong. He was apparently shagging someone and still proposed to me and took me on a filthy weekend.

I was heartbroken when I found out. I wish someone had told me what he was like - then I wouldn’t have wasted 19 years with the dirty weasel.

Id have been shocked, but I would have listened.

Get a new job, then get medieval on his ass.

You are out of the firing line and morally you have done the right thing by telling her. What happens after that is up to her.

You should tell her, and show her the evidence. Make sure she knows you had no idea he had a girlfriend and that as soon as you found out, your relationship with him stopped. So that she knows you're not doing it because he dumped you and you're seeking revenge, as that's the story he'll tell her, if he admits it.

She should know, then it's up to her whether she splits up with him, or marries then inevitably divorces him.

We're human our motivations are often complex, from your OP it doesn't sound like you just want to see him hurt. You also said you think she should know. It's very normal to feel both those things and you're not a bad person for wanting him to hurt for what he's done to you nor does feeling that mean you shouldn't tell her. PPs saying they would tell or wouldn't don't really know for sure until they're actually in that situation. A year ago I would have said I'd tell her, right now with everything I have going on I don't think I could cope with the fallout, especially given you work for the same company. It's not an easy black and white yes or no answer and while motivation does matter its not the only thing to consider when working out what to do.

Regardless of what your motive is for telling her - she deserves to know.

if I had a fiancé cheating on me I wouldn't give two hoots why she told me, and would just be glad to know about it.
Some women bury their heads in the sand and proceed anyway, but at least telling her gives her the option to leave. He was probably having sex with both of you so there was no informed consent for either her or you.

I think if your motivation is genuinely for her interest and not to get at him, then you should tell her, at least she can choose to marry him knowing what he's really like. I suspect this isn't the first time either given he decided to cheat on someone at work. What a prize pig, be glad you dodged a bullet!

I would

So you are doing it releive your guilt? It would be about you not her, and some people can have all the redflags in the world and it means nothing so again what do you hope other then putting yourself first?

I am going to be honest with you
I wouldn’t tell his fiancée.
I would put my head down , keep away from that man and start looking for another job.

My opinion is to do as you would be done by, although its a very good point that has been made about having proof....oh and if it was a physical relationship, get yourself tested too....you and his fiancee might not be the only ones.

What are you on about? 😂 so “yawn” but you still had to reply, huh?

It doesn’t matter if she forgives him or not as that has nothing to do with you, but she should still be informed.

There could be more - she needs to know so she can get tested, at the very least.

Can’t believe how many people say not to tell. The partner deserves to know her fiance is a cheating prick.

No. It will make work difficult for you if she’s friendly with colleagues.

Do tell her. She deserves to know before marrying the prick. I imagine you have text messages to back this up?

Nope. Don’t. I think this backfire really badly on to you. I understand the desire to tell her, bur honesty I’d focus on yourself. Start by looking for a new job and take this as lesson not to get involved with people at work!

this is why i have copies of all texts and watsapp etc

Honestly, no, I wouldn't.

What do you stand to gain? I can't see any way where this benefits you, but there is potential to make things worse.

Best case: she appreciates you contacting her, breaks of the relationship, he sculks of somewhere to another job and you get the satisfaction of knowing he fucked you around but he got his comeuppance.

But what are the chances of that?! Much more likely are any number of scenarios where a lot of unnecessary drama comes back at you. Especially since you work together!

Forget about him. Move on and thank your lucky stars it's not you marrying him