I'm actually quite amused that I'm being slightly attacked here. My gut feeling was to say nothing and I was looking to check that this was the general consensus and that I wasn't going to be doing the wrong thing by not saying anything.
To be clear, it is definitely the same guy. He remembers me from that trip, we have talked about the fact we were both on it. He may or may not realise that I was really good friends with the girl and he definitely did shag her that evening. As I say, I was not going to say anything , I just wanted to check that people were in agreement with this.
I have only just met his wife and I did not know that at the time he was in a relationship. At the time I was excited for my friend who had hooked up with him and she actually thought it was going to lead to a relationship when we all got home. She did see him a few times when we got back so it wasn't just a one night thing, but it was a short lived one.
Thanks for the comment, you are right, he may have come clean previously and they may have worked through it. He may well be bricking it now because he knows I know about his infidelity. So he may even come clean now.
I am not and was not intending to tell the wife anything. I was Just wondering whether I should tell my new friend and colleague the reason I'm not super keen on hanging out with them as it's bloody awkward! But don't worry I will keep my gob shut. You are right it would only come bad on me!