Some good points raised, thanks to all. I have realised I have nothing to gain by telling OW's H. Hopefully all this will trigger her into sorting out her own relationship.

I'm still trying to sort things with my H and it's a long and painful process.

I think in these types of situation the primary responsibility lies towards the children and protecting their right to a stable home environment. If they are very, very lucky that will be two responsible mature adults who are proper parents and also are also in love/love each other. That is the ideal scenario. Sadly, I think it is probably relatively uncommon.

So - next best scenarios - couple who live together providing a reasonable stable home environment but are not necessarily "in love" and my, possibly, think about other relationships or more, with or without knowledge of partner.

Couple who have reached a point where they can no longer live together to provide a reasonably harmonious environment for bringing up children - therefore decided to separate for a bit, maybe longer, maybe eventually divorce. Both parents maintain reasonabl relationship with each other for the sake of the psychological health of their children.

Other scenarios are less attractive.

In this particular case the husband is presumably not yet at a stage where he feels able to discuss the issues that have lead to the "triangle". However, removing the extra person from the triangle will not make the issues go away - just the symptom. Likewise, telling the other woman's husband will be precipitating a cascade of events - which may or may not lead to the "desired conclusion" whatever that is. Again, you can remove the lover from the equation but that does not resolve the underlying issues.

Also, if you "tell" you are taking on the role of judge and jury - you will most likely not be thanked for it - by anyone at all.

Abdelia: because you (generic 'you') don't know the OW or her husband and more importantly it's not your business. And barging in waving the monogamist flag has the potential to do far more damage than sorting out your own relationship and leaving other people to deal with theirs.
Shiner: 'being married' but being in a shitty marriage (for whatever reason it's shitty) is NOT an advantage, it's a prison sentence. It's perfectly OK to be single, and being single is always and inevitably better than being in a miserable relationship.

Hmmm, then again he might be on ADs owing to his wife's poor behaviour and denials. If they have an arrangement they'll ignore her. How can you discuss something you know nothing about, barring a massive feeling things aren't right. And what about his sexual health, if nothing else?

I think it would be very, very selfish to say anything to the other woman's husband. Totally wrong and selfish - for all everyone knows they have an "agreement", he has had affairs or there are other things going on. Their marriage/relationship has nothing to do with anyone else. Also, if there are children involved, then perhaps they have decided to "do their own thing" but keep a family unit. This is perfectly understandable. No-one should meddle in anyone else's relationships. The problems within a marriage or relationship are between the two people involved - that is where the discussions should be taking place - anyone else is there because someone in the relationship wants them to be. So the discussion needs to revolve around that issue with whoever wanted an extra person in the relationship. No good will come out of throwing sh** into someone else's family life - sometimes people have turned a blind eye - and it is their right to do so.

After much thought, I agree with Abedelia on this one. I feel very strongly now that keeping people in secrecy denies their choices in life and with hindsight, I now wish I had ensured OW's H knew, if only to let him know the truth about his wife before he had children with her.

If they had already had children, I suspect I would have still have kept quiet, but this time for the children's sake. Such a decision would also be affected by whether I thought the affair was ongoing - or had resumed - and also the behaviour of OW after the affair had been discovered.

The bit of your post OP that didn't resonate with me was when you said that you sometimes felt you didn't care...are you sure of your reasons for trying again?

I suppose I would be protecting my H if I didn't tell her H (no enraged man turning up on doorstep etc - especially if affair over). I don't know really I suppose, honesty is the way forward and I know I wanted to know about my H but to be the "messenger" of it all, I don't know......

Tough call Scodgie.

Just a quick alternative view to the 'don't tell the OW's husband' advice. I did let the husband know, and I am very glad I did. For one thing, I think he deserved the truth and should not be left living in the dark about what a delight his wife was. Turned out it wasn't the first time she'd done it, though in the previous case the OM lived in her home country so she couldn't actually arrange a PA, just an EA - and this also helped my H get over it very quickly as it was clear then that she'd lied through her teeth about herself and her supposed values. Her H even exposed a story about someone close to her dying that she'd used to bond with my H at the very start and on which much of the affair was built - all lies, think she was a bit of a narcissist really.

It is also much easier to ensure no contact takes place if there are two of you watching out for it. Personally, I'd always want to know if my partner was cheating, so yes, i applied my values to what I'd have wanted if I was her H. But that's up to you - this is just something to balance what othes have said.

I'm not disagreeing with all those who declare that divorce is the way ahead, but I would like to make a couple of comments before you choose that route.

Divorce is not automatically a means to a happier life. It is in itself hugely upsetting, and once you are divorced, you are left on your own. No-one else to help with your life, or with the children; rather, you have the added difficulty of helping your children come to terms with Daddy not being around any more.

I know several women of my age who are still looking for someone to appreciate them and make them happy. Singledom isn't filled with hoardes of available men waiting to demonstrate that they would be better. It's filled with rats and love cheats, men who are married or gay but don't tell you, and so on. It's hard enough when you are single to meet nice men, it's even harder when you are older/have a couple of children to consider.

Whilst you are still married to this highly imperfect man, you at least have one thing. You are married. And he is the father of your children. This is something. Maybe a starting point. Once you are divorced from him, you do not have even that.

I once worked for a lady who was going through a divorce. He played some dirty tricks on her, met other women and it was all a bit unpleasant. However, all these tricks slowed the proceedings down, and with time, they started to see that in fact they were better off staying together and rubbing along civilly than completing the divorce. 20 years later, they are still together, the children are grown up, and they look back on a bumpy life together. I would actually say they are happy.

All the best with whatever you decide; I hope you find a happy way to proceed.

Scodgie, expect your feelings to go from one extreme to the other. It sounds like your H has had a big wake call and hopefully has learnt his lesson. Think about going to Relate or similar, I found it helped having a third party, independent perspective on it all.

And FWIW, I would leave OW well alone (although it is tempting to reek revenge), I know she was equally responsible as your H but it is up to her whether she tells her H (if he finds out another way at least you know you had no part in his or her childrens' unhappiness if makes sense). I could have got the OW sacked from her job in my case but I took the view that she was a single mum and her kids didn't deserve the fallout (even though she and my DH had put my kids through hell). She managed to get the sack anyway though not through anything I did - karma always bites you in the bum eventually .

Good luck