I understand why you feel some level of discomfort at what you saw. Because this man is married and talks regularly about family life, you’ve clearly placed him in your head as ‘out of bounds’. Your tone, however, suggests that you are ramping up your judgment to a degree that I would normally only expect from the betrayed partner.

I am guessing that you are feeling somewhat betrayed by someone you had previously judged to have bucketloads of integrity. I can empathise with you to a certain extent. I once worked with a man I liked enormously who suddenly got fired because he had been discovered cheating on his expenses to a grave degree, and was effectively embezzling our company funds. Police were called in and the event was considered major within our company. I was completely blindsided when I found out and, for some reason, felt personally betrayed. I look back now and wonder why I had such a strong adverse reaction. After all, his thieving was nothing to do with me. But, like you, I had held this person in very high regard; I had seen him as a friend and confidante as well as a colleague, and I felt stupid for not realising he was actually just a dishonest, small-time crook. I had totally misjudged his character.

I know that your colleague’s behaviour may have shaken your moral compass somewhat, but before you cast him out as a pariah you need to ask yourself this simple question: why is this any of my business?

Honest Boss: “I saw my colleague cheat on their partner at a work event. Should I say anything?”