What advice to give?

Well, if she hadn't looked at his phone messages she might never have known. She must have had suspicions to want to see whether they were correct? She can confront him about her original suspicions.

Or she can fib and say that his phone rang and she answered it in case it was urgent and "happened" to see the messages.

She can ask detailed questions about his outing on his own last night and try to catch him out.

She can tell the truth and risk his anger at her checking his phone - though if she already had reason to doubt him she can try justifying it with them.

However she decides to tackle it, she needs to ask herself if he is really the one if he is prepared to deceive her, and whether she really wants to continue this flawed relationship at all costs. If so, it might be better to keep schtumm and consider just why she is not enough for him, and why he has strayed elsewhere? Is it his fault or hers? With a history of failed relationships, there may be a common factor in all the failures. You might find that telling her this doesn't go down too well, of course, what she wants is your sympathy and support right now, not the Dutch Uncle approach.

When I was younger I wanted all relationships to be exclusive and certainly marriages should be so I feel. However as I grow older I feel that if I was in the position of dating someone rather than living with them and exclusivity had not been agreed not just merely tactility expected I think it might be acceptable that one or both of you see other people. I am uncertain about the nature of your friends relationship.

As to advising a friend I just wouldn't do it if I wanted to keep the friend-just tea and sympathy.

I spent ages advising a friend to kick him out only for a big reconciliation to happen and I was the worst in the world , tea and sympathy and non committal answers /advice

Don't give her any advice. Just be there for her and support any decision she makes even if you don't agree with it.

Don't give any advice, but do listen, without interrupting, to what she has to say.

Whatever advice you give, she will do what she wants to do in the end. It may come back to bite you at a later date if you say something she doesn't want to hear.

Just allow her to use you as a sounding board and be there with team cakes, tissues and a hug.

Don't advise and don't pre-judge her situation.
Ask 'open' questions which will help her see things from different view points.

I wouldn't give opinions or advise just be there with plenty of tlc for when she needs it and it sounds as though she will,it sounds as though he is having his cake and eating it at the same time he will soon be found out.

Depends on how good a friend she is, with what advice you give but chances are she won't listen anyway.

Elegran....she can't really say she answered a fictional incoming call because the Call Log shows the call history.

I think that she really only wants to know about the confronting bit. Nothing else.

She may have to say things like
"Do I smell perfume on you"?
"You are looking guilty/shifty."
"Is there anything I should know?"
"You were later home than normal" type questions. Assuming they are true.

She is not going to listen to anything else. She hasnt in the past about this matter. And not likely to in the future.

Loads of really good advice here! Definitely a three monkeys situation. See all, hear all but say nothing. Offer lots of [cupcakes] as seems appropriate. Good luck!

I don't offer advice normally, but she has specifically asked me what I would do, we have always been honest with each other. I have always been there to support her (as she has been for me in the past) and she knows I will be there for her no matter what decision she makes. I just hate to see her making the same mistakes - she is a lovely trusting person who would help anyone in trouble and doesn't deserve to be treated in this way.

My advice is not to give advice! - people's relationships are a minefield and we can never know what really goes on inside them.

Just be a good friend.

If you give advice and it turns out to be advice she doesn't really want, you will be the 'bad guy'. If, as you say, she has been there before, she should know the score. Leave her to it and just be there to listen and provide a shoulder to weep on, if that's her way.

Just listen and be a good ear and a shoulder to cry on (for a while).

She has the facts.....she does not want to 'loose' him (moot point as to whether she 'has' him however.

But seriously, she has a problem but seems to have already made her choices - by asking you for your opinion she might just be wanting you to make it all alright in her mind....sort of agreeing that she's right.

Whatever happens if you say 'stay' and he is the man you think he is you will be wrong.....if you say 'confront or leave him'....and he changes (huh......does that ever happen?) you will still be in the wrong.

Just say....'I will be a sounding board...but you have to choose'..... to be honest only those within a relationship know how it is (up to a point). You are working on the facts according to her....so that's a minefield.

I know the sensible thing is not to give advice but if a dear friend specifically asked me what I would do I would tell her: I would come clean and tell the man that I had checked his phone, and I hope I would have the courage to end the relationship.

I don't think I could forgive a cheat and a liar or ever be able to fully trust the person again. However, I would tell my friend that only she can know whether such a betrayal would have a permanently corrosive effect on her relationship or if she would be able to put the hurt behind her. (Anyway, perhaps the man wanted to be found out but didn't have the guts until this moment to finish it)

Well, she confronted him. Told him she had been told by a friend that he was having an affair. He, of course, denied it and demanded to know which friend, when she wouldn't say he then said it must have been me because I wanted to split them up - even suggested that I wanted him for myself!! That was his big mistake, it opened her eyes at how easy it was for him to lie to her so she told him she had checked his phone and that was how she knew. He claimed it was a mistake and a one off and would not happen again. After an argument he took himself off to the pub telling her she needed to think about where she wanted their relationship to go!

She rang and told me she has moved his things into the spare room and when he gets back will tell him she wants him out within a week. She even laughed and said she knew thats not what I would have done (I would have thrown his stuff out in the rain and locked the doors!). I suggested she stay with me until he has gone but she is OK with staying in the house with him. Thanks everyone for your replies

Infidelity is a touchy subject and there are those who can forgive and those who cannot. However, what it all really comes down to is the loss of trust not the actual 'act'. If someone can look you in the eye and lie and lie....then I do believe they have stepped over a line that cannot be redrawn. Trust is the bedrock of any relationship and without it nothing else can survive.

Your friend has been brave, and she's probably right to stay put if she can cope - he is obviously not to be trusted and could cause great inconvenience by being obstructive in her home. Its great she has your friendship - she's going to need a fair bit of support now. All the best.