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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Partner lied to me about his best friend cheating

77 replies

Rubylu · 08/01/2026 16:42

I’ve recently found out my partners bestfriend was having an affair on his girlfriend. I asked my partner multiple times if they had split up, he kept telling me he knew nothing (even though it was completely obvious).

I then got told from a friend that they’d split up because he’d cheated on her, I asked my partner again to which he said he still didn’t know anything about it and his best friend wasn’t telling him anything.

My partner has now since told me that he did know he was cheating for the months he was doing it, he didn’t tell me as his friend had asked him not to incase I messaged his girlfriend and told her what he was doing.

Their Relationship is NONE of my business. I am not angry that I didn’t know the details, I am angry that he has lied to me, to my face multiple times especially when I’ve asked him repeatedly. His argument is that he was trying to be a good friend and he isn’t a “gossip”. I told him a good friend shouldn’t come at the expense of lying to my face for months.

Once I knew they’d split up I was going to message the girlfriend and just say always here if you need a chat, we get on really well have been on holidays together etc, he steered me away from it saying it isn’t my business. He then admitted to me he told me to not to message her incase she told me that he’d knew all along…

I just feel like I can’t trust him now? I understand it’s his best friend but we have 2 kids together, if it’s that easy to lie to me, what else is he lying about? I trusted him wholeheartedly and this has really threw me off

OP posts:
BootsIO3 · 08/01/2026 16:44

Not everything needs to be shared

TY78910 · 08/01/2026 16:48

Agree with @BootsIO3
He will have his reasons, maybe he was scared you’d tell the partner
Not justifying the scenario here but like you said their relationship is none of your business so he was likely allowing his friend to work out his relationship himself without 3rd parties
Doesnt automatically mean he will lie to you about your own issues

DeedlessIndeed · 08/01/2026 16:48

I really hope none of my friends ever put me in this position as I abhore all cheats. However, I wouldn't share the details of my friends affair with my partner if I had a hunch that my partner would say anything.

DH is great for keeping schtum, so I would probably tell him in a way to get it off my chest IYSWIM? But he wouldn't care either way as it really isn't any of his business;

So if your DP sees you as a gossip or someone who is close to GF/ gets mixed up in drama then I can see his reasoning for not sharing. Perhaps the fact you are unhappy about not being told is an indicator that you do get a bit involved?

Rubylu · 08/01/2026 16:50

@DeedlessIndeed i would not of told her and he knows that, I get on with her but she isn’t a close friend, if she was then I would tell her.

Once I’ve been told by someone else i already know the information anyway, so he had no reason to continue lying to me for a further month

OP posts:
PevenseygirlQQ · 08/01/2026 16:52

Rubylu · 08/01/2026 16:50

@DeedlessIndeed i would not of told her and he knows that, I get on with her but she isn’t a close friend, if she was then I would tell her.

Once I’ve been told by someone else i already know the information anyway, so he had no reason to continue lying to me for a further month

Maybe he didn’t want to put you in the position of knowing and then having to lie to the woman.

Snowingtoday · 08/01/2026 16:53

You partner has shown that not only is he a liar he doesn't have a problem with cheating. He not only maintained a close friendship with a cheat he actively aided and abetted his friend's behaviour.

I would never be able to trust him. How do you know, or how will you ever know, he isn't cheating on you and lying to you about it.

SugarCoatSandwich · 08/01/2026 16:54

Why were you asking if they split up in the first place?

Rubylu · 08/01/2026 16:56

@SugarCoatSandwich It was very obvious from social media

OP posts:
shropshire11 · 08/01/2026 16:57

Take the easy path here. You've admitted that you're not close to this couple - let them live their lives and don't make it into a drama about yourself.

juice92 · 08/01/2026 16:57

There will be reasons why he decided not to tell you. As others have said, maybe he didn't want to put you in a position where you had to lie, or maybe they was simply other stuff going on.

I generally tell my husband everything but I can remember once a friend telling me something and asking me specifically not to tell my husband. So I didn't. During that time I spent a lot of time on the phone with said friend and when my husband asked what was going on I just kind of shrugged it off - similar to what's happened here.

It wasn't my news to tell and it wasn't his news to tell you.

Espressosummer · 08/01/2026 17:01

Why did you pester your partner repeatedly about this when you say you don't think the relationship was any of your business?

Espressosummer · 08/01/2026 17:04

Snowingtoday · 08/01/2026 16:53

You partner has shown that not only is he a liar he doesn't have a problem with cheating. He not only maintained a close friendship with a cheat he actively aided and abetted his friend's behaviour.

I would never be able to trust him. How do you know, or how will you ever know, he isn't cheating on you and lying to you about it.

Edited

Very dramatic post and not borne about by the OP's posts. "Actively aiding and abetting" would be something like providing an alibi so the cheat could meet his mistress - the OP hasn't mentioned anything like that. You also don't know that he doesn't have a problem with cheating - he could have told his friend to end the affair.

JHound · 08/01/2026 17:06

I get why he would not tell you as you would tell his girlfriend blowing up the situation.

But I get your anger and his repeatedly lying to your face. Seems like he wanted to protect his scumbag friend above all. I may have told my friend I cannot lie to my partner so cannot be around them if they intend to cheat.

Rubylu · 08/01/2026 17:06

Espressosummer · 08/01/2026 17:01

Why did you pester your partner repeatedly about this when you say you don't think the relationship was any of your business?

It’s very wide knowledge they’ve split, even my sister in law (on partners side) came to me and told me the ins and outs of the split. So it just baffled me that my partner didn’t know anything from his best friend, I think deep down I knew he was lying hence why I kept asking him

OP posts:
JHound · 08/01/2026 17:06

How did your partner discover the cheating.

Rubylu · 08/01/2026 17:08

@JHound His friend told him it was happening, almost like an achievement from what my partner has said

OP posts:
JHound · 08/01/2026 17:09

Rubylu · 08/01/2026 17:08

@JHound His friend told him it was happening, almost like an achievement from what my partner has said

I honestly don’t think I could continue a friendship with a man like this and surprised your partner can.

I would also be LIVID if a friend put me in this position by coming to me to brag about their affair. What a weasel.

Inapickle3012 · 08/01/2026 17:10

How are you making their break up about you?

shouldofgotamortage · 08/01/2026 17:10

Your making their drama about you. How ridiculous.

mumstheword1x · 08/01/2026 17:12

if you hadn’t asked, I can understand why he wouldn’t tell you- but the fact you asked and he has lied to you on multiple occasions, would ring alarm bells to me. I can’t stand any type of lie, even a white lie.

and who protects a cheat?????

Rubylu · 08/01/2026 17:14

mumstheword1x · 08/01/2026 17:12

if you hadn’t asked, I can understand why he wouldn’t tell you- but the fact you asked and he has lied to you on multiple occasions, would ring alarm bells to me. I can’t stand any type of lie, even a white lie.

and who protects a cheat?????

This is exactly my thought process, to not tell me is one thing but to lie to me repeatedly is another

OP posts:
Snowingtoday · 08/01/2026 17:18

Espressosummer · 08/01/2026 17:04

Very dramatic post and not borne about by the OP's posts. "Actively aiding and abetting" would be something like providing an alibi so the cheat could meet his mistress - the OP hasn't mentioned anything like that. You also don't know that he doesn't have a problem with cheating - he could have told his friend to end the affair.

Not borne out by OP's posts? She said :

I told him a good friend shouldn’t come at the expense of lying to my face for months.

And of course he was aiding and betting his friend. If he had an ounce of moral decency he should have been at the very least cooling his friendship with this guy when he knew he was a cheat. And by not telling his friends g/f and lying to OP in case she had had the decency to let the g/f know then of course he was aiding and betting the cheating.

I feel very sorry for the g/f . She must be devastated to find out not only was she being cheated on but that it was common knowledge and no one gave her the heads up. The poor woman.

OP knows her partner has no hesitation in lying to her face. No doubt if her partner also cheats on her she will be the last to know given the lack of decency in the friendship group.

outerspacepotato · 08/01/2026 17:18

Your partner is ok with his buddy abusing his gf. Cheating is emotional, mental, and physical abuse and possibly financial. That's a big red flag as to your partner's lack of character. He lied to you to cover up for his buddy. Another big red flag.

Open your eyes to the people around you. If they do it to others they will do it to you. Your partner already lied to you multiple times to protect an abusive friend.

CinnamonBuns67 · 08/01/2026 17:20

I wouldn't appreciate my partner lying to me about it either. He could have said sorry but he wasn't able to tell you as he promised friend to not speak about it to anyone and for you to please stay out the situation. Yes he wouldn't have shared it with you and therefore kept his promise to his friend, but he wouldn't have lied to you about it either.

noidea69 · 08/01/2026 17:21

Rubylu · 08/01/2026 16:50

@DeedlessIndeed i would not of told her and he knows that, I get on with her but she isn’t a close friend, if she was then I would tell her.

Once I’ve been told by someone else i already know the information anyway, so he had no reason to continue lying to me for a further month

you wouldnt have told her, but you would have gone on and on about it to your partner and maybe he just didnt want to hear all your thoughts on his friend and the relationship that has nothing to do with either of you.