Changed my name for this in case it's in any way outing. So recently I've started a new job, I'm really enjoying it and the people seem lovely, but on my first day I was introduced to one of my new colleagues- who turned out to be someone I already knew and had worked together in a different organisation. To cut a long story short, he'd befriended me when I joined, then ramped it up to flirting (end stage of which saw him escalate to sending me explicit photos of himself)- I then found out on a work night out that not only did he have a fiancé, but he'd also been trying it on with half the office. We both left for different jobs in different organisations not long after that.
Fast forwarded to present day- when we were 'introduced' the other day, we both said a flat 'hi' with no other pleasantries but neither of us admitted to knowing the other. But now I'm worried this is going to come back to bite me- it seems our work is quite interlinked, he was noted on my job handover as someone to have a meeting with (I reached out via email and said feel free to send me what I need to know via email instead- which he did). I'd say I've been 'coldly professional'. Lots of people keep asking me if I've met/spoken to him and I just say no.
Please help me out with some advice on how to handle this carefully- I appreciate he's probably worried I'll tell everyone what he did but the last thing I want is for that to get out. But I'm worried that someone's going to figure out we worked together at the same place, work in the same location and department now- yet apparebtly have never met and clearly avoid all contact. I'm also worried that I'm avoiding contact about work-related things because and I want to do my job well. How do I handle this?