A lot of posters seem to forget that Boriso has been quite happy for her dh to conduct a friendship with this woman for the last twenty yeaars. It is only NOW that she knows they have snogged she has stopped him from visiting her. That is worth bearing in mind when you talk about lack of freedom in a relationship and how suffocating might lead to temptations. Borisa has given her man freedom, and he has abused it.
Boriso, I hope you get a chance to really sit down and talk, and that your dh figures this out in his head. I have sort of been in your dh's position. It was over a year ago. Our relationship was not good, but I doubt my dh knew it, as I did not talk to him about how I felt, but somebody else. It is very easy, when you start talking about your unhappyness, to get carried away and see things in the other person you did not see before. In my case, I felt unloved, unnoticed, and my dh rarely had time for me. It was a short temporary infatuation. I was lucky that I managed to figure it out in my head before doing something really stupid. But it did enable me to sit down and talk with my husband, in a very honest way, and we did manage to put our relationship back on track. The last year has been much better, I love my husband very much, and he me, and sometimes you "forget" you love your spouse when you allow another person to interpret your relationship for you, tell you your partner is crap, you have to split up as there is no hope, etc. Yes, it was my fault for sharing confidences with another person in the first place and so putting myself in this position. But sometimes, when you seek somebody to talk about your own relationship to get a fresh perspective and maybe help to sort something out, you get something else than you bargained for. Especially if the other person has his own "designs on you".
What I am trying to say is, your dh is not necessarily a twunt, and it IS possible to save your marriage, but you have to trust that he is not in touch with her. If he still is, that is bad. He should be able to see that he wants to be with you, and he should be so scared to actually lose you he would be frightened of her calling him, or be thought to be in touch. If he is unwillin to give up on her for the sake of their long friendship, that speaks volumes, as it has moved passed friendship. They are not friends any more, and they can never go back.