Well yes, the Head of Department that oversees all of us would listen to him regarding appraisals etc but I don't think he would be saying anything bad about me as I good at what I do there. Also there's little chance of promotion as it's a very, very small company. From their emails, I gather she is looking to go in about six months anyway so I guess I will just ride it out til then!
We have one HR lady and to be honest, I don't want to raise it with her as she will no doubt raise it with the Head of Department.
It's very common (but disgraceful). Shameful behaviour from both of them, him obviously cheating on his wife and her showing a complete lack of humanity.
1) Do you know the man's wife - are you friends with her?
2) re you worrying about your main boss - if they are legitimately away on business and are shagging each other whilst away, that isn't actually costing the company money or time. Presuming that the co will have paid for hotel/meals anyway and they will not be at it during business hours. So have you any reason to think that they are abusing company money/time?
If no to both, you don't need to feel conflicted in completely ignoring this affair.
2) Sorry I don't think I was clear. I am saying that he can use the excuse of: Oh I'm away on business to his girlfriend to then go and shag the girl from work in a hotel. I know about the hotel stuff as that's the email that I stumbled upon on the company emails!